ROAD RESEARCH LABORATORY

M in istry or,Transport

RRL REPORT LR 343

A BIBLIOGRAPHY WITH ABSTRACTS OF

RESEARCH INTO THE USE OF POLARISED HEADLIGHTS

by

L. Cooper

Driver Aids and Abilities Section

Road Research Laboratory

Crowthorne, Berkshire

1970

.C ONTEN TS

Abstract

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2.

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Int roduc t ion

R e p o r t s by Road R e s e a r c h L a b o r a t o r y

R e p o r t s f r o m other s o u r c e s

Some m e n t i o n s of p o l a r i z e d l ight o ther than

at R R L

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Q ' : CROWN COPYRIGHT 1970

E x t r a c t s f r o m f h e fext m a y be r ep roduced p rov ided .the .source -is acknowledged

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Ownership of the Transport Research Laboratory was transferred from the Department of Transport to a subsidiary of the Transport Research Foundation on l S t April 1996.

This report has been reproduced by permission of the Controller of HMSO. Extracts from the text may be reproduced, except for commercial purposes, provided the source is acknowledged.

A BIBLIOGRAPHY WITH ABSTRACTS OF RESEARCH INTO THE USE OF POLARISED HEADLIGHTS

ABSTRACT

Research undertaken at RRL since the first report was issued in 1949 is described by means of an annotated bibliography. Reports issued from other sources, together with a selected list of pertinent references, are given in a separate annotated bibliography.

1. I N T R O D U C T I O N

This paper provides an annotated bibliography of relevant material on the use of polarised light for vehicle headlamps. References to research undertaken at the Road Research Laboratory and elsewhere are documented separately.

. R E P O R T S B Y

R O A D R E S E A R C H L A B O R A T O R Y

Year 1949

i. JEHU, V.J. Polarized pass lights. Department of Scientific and Industrial Research, Road Research Laboratory Research Note No. RN/II92/VJJ. Harmondsworth, 1949 (Unpublished).

The feasibility of using polarized light in the passing beam only, and retaining ordinary light for the headlight is discussed. It is shown that with such a system without special high power lamps, visibility distances when meeting vehicles travelling in the opposite direction would probably be considerably higher than those now obtained with passing beams using ordinary light, with the added advantage that glare from the opposing lamps would be almost entirely eliminated.

The responsibility for switching from the normal headlights to the polarized pass light would rest with the driver, but on busy and fairly busy roads the polarized pass light would probably be used

continuously, so that switching should not become •irksome.

In order that the maximum benefit should be obtained from the proposed system, it would probably be necessary to replace the toughened glass windscreens now in use with the laminated type of screen.

Difficulties would remain for pedestrians and cyclists. It should however be possible to give them some degree of protection even without the use of polarizing spectacles by using a beam having a low intensity in the offside upper portion.

Year 1953

. ANON. Factors in the improvement of headlamp performance. Serv. Station, 1953, 29 (5), 26-8, 70; (6), 22-6, 35.

The paper describes experimental work carried out at the Road Research Laboratory and is presented as follows: i. Correcting misaim, reducing dazzle. Performance of beams, misaim, deterioration, polarized light. It is considered that there is little to choose between the various modern well-designed headlamps when they are correctly aimed but the effects of misaim and deterioration are more serious for lamps with sharply defined beams than for others. The double-dipping lamp now being fitted on a large proportion of new cars in Great Britain is one of the best as judged by range of vision, distance, general illumination, and freedom from glare. Recommend- ations are being made with a view to obtaining a greater uniformity of vehicle lights. 2. Headlight testing equipment. Five common types of beam testing equipment have been examined at the Laboratory for

accuracy and convenience in handling and the results are reported.

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3. HARRIS, A.J. Dazzle, visibi'lity, and suggested measures ~' which might be taken to improve the performance and reduce the glare of the meeting beams of vehicle headlights. Department of Scientific and Industrial Research, Road Research

Laboratory Research Note No. RN/1828/AJH. Harmondsworth, 1953 (Unpublished).

The report reviews work, done at the Road Research Laboratory and elsewhere, on the main factors whichdetermine the distance at which an object can be seen by a driver in the light of his dipped headlights when approaching another vehicle at night.

The use of polarized light is not discussed at length. It appears, however, to provide the only form of vehicle lighting yet thought of by which an escape may perhaps be made from the limitations imposed on the ordinary meeting beam by misaim, vibration and deterioration. (Shortened Author's summary).

Y e a r 1 9 5 4 ~.

. HARRIS, A.J. Vehicle headlighting: visibility and glare. Department of Scientific and Industrial Research, Road Research

Technical Paper No. 32. London, 1954 (H. M. Stationery Office).

This paper reviews work undertaken at the Road Research Laboratory, and elsewhere on the main factors which determine the distance at which an object can be seen by a driver in the light of his dipped head- lamps, when approaching another vehicle at night. The main results are also presented of comparative tests undertaken by the Road Research Laboratory, and made with a number of different meeting (passing) beams to determine which is the most generally acceptable. Investigations on the condition of vehicle headlights on roads in Great

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Britain are described and the effect of misaim and deterioration on

performance is examined on the basis of the available information.

Consideration is given to the steps which might be taken to improve

conditions, and it is concluded that as far as conventional headlighting

is concerned the essential need is to attain a uniform standard of

lighting on all vehicles; the limits to the improvement attainable in this

way are examined. A considerable improvement over present conditions would be achieved by the elimination of defective and inefficient lamps

and by ensuring that the remainder were properly aimed; The use of

a single design of meeting beam is thought to be desirable. Measures

are discussed which are designed to improve aim and performance but

it is noted that even under the best conditions the range of vision would

still be too restricted to allow safe driving at speeds which are now

cbmmon. It is considered that, broadly speaking, only a very limited

and variable standard of vision is possible unless the present type of

lighting can be replaced by something radically new. The advantages and disadvantages of polarized light are mentioned. An appendix

contains information about the theory of the probability calculations by

which the effects of beam pattern, misaim and deterioration were e valuated.

Y e a r 1955

. JEHU, V.J. Polarized headlight filters. Department of

Scientific and Industrial Research, Road Research Laboratory

Research Note No. R_N/2536/VJJ. Harmondsworth, 1955 (Unpublished)

I f a n o b j e c t w h i c h i s n e i t h e r v e r y l i gh t n o r v e r y d a r k is to. a p p e a r as b r i g h t in p o l a r i z e d l i g h t , w h e n s e e n t h r o u g h the v i s o r , as i t n o r m a l l y . a p p e a r s i n u n p o l a r i z e d l i g h t , , a b o u t f i v e t i m e s as m u c h .light i s n e e d e d . W h e n the t r a n s m i s s i o n a n d e x t i n c t i o n c o e f f i c i e n t s of t h e p o l a r i z i n g . m a t e r i a l a r e k n o w n , i t i s p o s s i b l e to c o m p a r e t h e p e r f o r m a n c e . o f a

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polarised headlight system with that of systems using ordinary light, in terms of the seeing distances of a standard object. A high intensity polarized beam can only be used if the beam is almost completely polarized. At lower beam intensities less stringent demands are made on the polarizer.

T h e e x t i n c t i o n of o n c o m i n g p o l a r i z e d l i g h t s by t h e v i s o r d e p e n d s u p o n t h e a c c u r a c y of i t s s e t t i n g , and m a y a l s o be i n f l u e n c e d by t h e p r o p e r t i e s of t h e w i n d s c r e e n . F o r a p a r t i c u l a r p o l a r i z e r t h e l i g h t l e a k a g e w a s i n c r e a s e d on t h e a v e r a g e 150 t i m e s f o r a t o u g h e n e d g l a s s w i n d s c r e e n a n d f o u r t i m e s f o r a l a m i n a t e d g l a s s s c r e e n . I t is e v i d e n t t h a t e x i s t i n g t y p e s of t o u g h e n e d g l a s s w i n d s c r e e n c o u l d n o t be u s e d w i t h p o l a r i z e d h e a d l i g h t s , u n l e s s the v i s o r w e r e m o u n t e d o u t s i d e t h e w i n d s c t e e n .

. JEHU, V.J. Some polarized headlight sYstems. Department of Scientific and Industrial Research, Road Research Laboratory Research Note No. RN/2624/VJJ. Harmondsworth, 1955 (Unpublished).

The note discusses the widely differing proposals that have been put forward in America and Germany for the use of polarized headlights, and records the results of tests made with an alternative system.

Any polarizing device fitted to a headlamp will reduce the light available for seeing. The American system overcomes this handicap by increasing the power of the polarized headlights, so that the user always sees at least as well as with the driving beam of conventional headlights; the German system on the other hand uses a polarized beam which is no more glaring to face without a visor than existing German meeting beams. Neither system would be easy to introduce, because initially the benefits to the user would, for different reasons, be limited to the occasional meeting with another user.

Polarization of •existing driving beams would provid.e a system which operated between these two extremes, and would enable the user to s e e o b j e c t s in h i s own b e a m a t g r e a t e r d i s t a n c e s t h a n u s u a l e v e n w h e n m e e t i n g n o r m a l b e a m s . D r i v e r a p p r e c i a t i o n t e s t s w i t h t h e s y s t e m , h o w e v e r , s u g g e s t t h a t i t d o e s no t i l l u m i n a t e t he r o a d n e a r t h e , v e h i c l e w e l l e n o u g h to i n s p i r e c o n f i d e n c e , a n d t h a t t h e l o s s in s i l h o u e t t e s e e i n g is a r e a l d i s a d v a n t a g e . P r e l i m i n a r y e x p e r i m e n t s s u g g e s t t h a t b o t h c r i t i c i s m s m i g h t b e o v e r c o m e in a p a r t l y p o l a r i z e d s y s t e m , in w h i c h

the near view is illuminatedby unpolarized light and the distant view by polarized light.

Year 1956

. JEHU, V.J. An assessment of polarized headlighting. Int. RdSaf. Traff. Rev., 1956, 4(i), 26-31.

The theory of a plane polarized light system is briefly described, and a comparison is made between the U.S. and German systems of polarized headlighting. The proposed U.S. system uses a beam with a Polarized light intensity of i00 000 cd, the headlamps having 125-W filaments. In the German system the meeting beam, which is supplied by two additional lamps with 50-W bulbs, is polarized and aimed so that it is no more giaring than existing meeting beams. Two alternative systems are outlined: (I) Special polarized lamps can be fitted in the German manner, and the normal headlights retained for open-road work, the polarized beams being aimed in a predetermined way such that the forward beam intensity is considerably in excess of that of normal meeting beams. (2) The open-road beam of existing headlights can be polarized. In both cases spectacle analyzers or visors can be used by the driver. The advantages of the second of the alternative systems are mentioned and an account is given of tests carried out at the Road Research Laboratory, Harmondsworth, in which drivers were asked to compare this polarized system, the headlamps being set in various ways, with normal unpolarized meeting beams: both wet and dry road surfaces were used. Results are presented and discussed. Additional tests are mentioned in which five cars were equipped with polarized driving beams and normal meeting beams, three of the polarized beams being British driving beams and the other two German beams aimed With their maximum intensities straight ahead; test runs were arranged so that one car met the other four. Exploratory work was also carried out on a partlypolarized beam, by fitting auxiliary

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l a m p s to t h e c a r s w i t h p o l a r i z e d B r i t i s h d r i v i n g b e a m s to p r o v i d e a w i d e f a n of u n p o l a r i z e d l i g h t d i r e 6 t l y a h e a d o f th e vehicles. T h e main~ ~" ~' g e n e r a l c o n c l u s i o n is t h a t t h e t e s t s c a r r i e d ou t so f a r h a v e n o t r e ~ e a l e d a n y c o m p l e t e l y s a t i s f a c t o r y a r r a n g e m e n t bu t t h e y i n d i c a t e t h a t t h e p a r t l y p o l a r i z e d b e a m s h o u l d b e f u r t h e r i n v e s t i g a t e d .

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L ~ r . . . .

JEHU, V.J. Polarized headlight filters.

S0c.~;Lond., 1956, 21(7), 149-59.

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Trans. illum. Engn~

One way of reducing the glare from headlamps is to use. a polarized

headlight system. In this paper the relative merits, for this purpose ....

of commercially available, filters are discussedl A second paper will ~

discuss the widely differing proposal s that have been put forward in

America and in Germany for the use of polarized headlights,~ and .gives the r e s u l t s o f t e s t s m a d e w i t h an a l t e r n a t i v e s y s t e m . ..

If an object which is neither• very light nor very dark is to appear

as bright in polarized light, when seen through the visor, • asit normally

appears in unpolarized light, about five times as much light is needed. ~

When the transmission and extinction coefficients of the polarizing

material are known, it is possible to compare ~he performance of a

polarized headlight system with that of systems using ordinary •light,"

in terms of the seeing distances of a standard object. A high intensityi'

polarized beam can only be used if the beam is almost completely

polarized. 'At lower beam intensities less stringent demands are mad~

on the polarizer.

The extinction of oncoming polarized lights by the visor depends

upon the accuracy of its setting, and may also be influenced by the

properties of the windscreen, l?or a particular polarizer the light

leakage was increased on the average 150 times for a toughened-glass '

windscreen and four times for a laminated-glass screen. ~ It is •evident

that existing types of toughened,glass windscreen could not be •used

with polarized headlights, unless the visor were mounted outside•the

winds creen.

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9. JEHU, V.J. Some polarized headlight systems. Trans. illum.

Engng Soc., Lond., 1956, 21(7), 160-7.

This paper discussed the widely differing proposals that have been put

forward in America and Germany for the use of polarized headlights,

and records the results of tests made with an alternative system. The

discussion and tests are concerned only with the benefits to drivers of

vehicles. The consequences to pedal cyclists and pedestrians are not

discussed in this paper.

Any polarizing device fitted to a h eadlamp wiU reduce the light

available for seeing. The American system overcomes this handicap

by increasing the power of the polarized headlights, so that the user

always sees at least as well as with the drivingbeam,of conventional

headlights; the German system on the other hand uses a polarized

beam which is no more glaring to face without a visor than existing

German meeting beams., Neither system would be easy to introduce,

because initially the benefits to the user would, for different reasons,

be limited to the occasional meeting with another user.

Polarization of existing driving beams might provide a system

which operated between these two extremes, and might enable• the user

to see objects in his own beam at greater distances than usual even

when meeting normal beams. Driver-appreciation tests with the system,

however, suggest that it does not illuminate the road near the vehicle

well enough to inspire confidence, and that the loss in silhouette seeing

is a real disadvantage. Preliminary experiments suggest that both

criticisms might be overcome with an in-part polarized system in

which the near view is illuminated by unpolarized light and the distance

view by polarized light.

10. • JIEHU, V.J. Night driving could be easier. A constructive

outlook on .the problem of dazzle. Motor, Lond. , 1956,• i,i0 (2855),

809-12.

Factors which make night driving difficult include the wide variety of

lamps met, flashing and dazzle. Correct aiming of headlights would

eliminate much of the dazzle and a simple apparatus is described

which would allow any garage to adjust headlamps correctly. Proper

aiming would also help oncoming traffic by silhouetting other road

users and would make automatic dipping of headlights practicable;

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.greater use of headlights in poorly-lit streets could be encouraged and the marking of obstructions by reflectorized material would be possible. If headlights were correctly aimed, one or other of two major improvements might follow, either a more sharplydefined meeting beam or the introduction of a polarization system.

Ii. MOORE, R.L. Headlight design. Department of Scientific and Industrial l~esearch, Road Research Laboratory Research Note No. RN/2873/RLM. Harmondsworth, 1956 (Unpublished).

A brief survey is given of the historical development of motor vehicle headlights. The principles underlying the design of the block lens headlamp used in America and Great Britain and the sharp cut-off lens used on the Continent are described and a comparison is made of the two systems.

An outline is given of t h e polarized headlamp s y s t e m t h a t is being investigated by the Laboratory.

4.

Year 1958

12. MOORE, R.g. Headlight design. Ergonomics, 1958, l(Z), 163-76.

A brief survey is given of the historical development of motor vehicle headlights. The principles underlying the design of the block lens headlamp used in America andGreat Britain and the sharp cut-off lens used on the Continent are described and a comparison is made of the

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two systems.

An outline is given of the polarized headlamp system that is being investigated by the Road Research Laboratory; the light emitted in a direction which might cause dazzle is polarized but the light falling on the road near the vehicle is unpolarized. It is concluded that (I) with equipment now on the road, a very substantial improve- ment in visibility and dazzle could be obtained by improving headlight aim and restoring or replacing damaged lamps; (Z) no great improve- ment is possible by a change of lamp design using ordinary light; (3) the most hopeful field of enquiry is the use of a polarized headlight

system.

Year 1960

13. GLANVILLE, Sir W. Light and road safety. Trans. illum. Engng Soc., Lond., 1960, 25(2), 69-85.

A review is presented of the work of the Road Research Laboratory, Harmondsworth, on street and vehicle lighting and attention is drawn to a number of problems which have yet to be resolved and to many practices where improvement is possible. The main subjects covered are as follows: revealing power and the effect on it of changes in the road surface or in the lighting installation; the relation between the light-reflecting properties of the surface and its texture and colour; street lighting lanterns and the isiting of columns; the economic benefits, the effects on accidents and speeds, of improved street lighting; an experimental low-cost lighting system for non-urban main roads; the performance of headlamp meeting beams; the adjustment and maintenance of headlamps ; the comparis on of yellow and white beams; the use of polarized beams; the design of foglamps; the investigation of vehicle rear lights, reflectors and direction indicators.

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14. GRIME, G. Automobile lighting and visibility. Crompton -

Lanchester Lectures, No. I0. The private car. Institution of Mechanical Engineers, Automobile Division. London, 1960

(Institution of Mechanical Engineers), pp. 154-66.

The lecture deals with features of the car •which aid the driver in

receiving visual information about the road and the traffic on it, and

about the intentions of other drivers.

The shape and extent of .the glass areas of the vehicle are of

obvious importance and a summary is given of recent work on the

view in the forward direction from modern cars, and on the design

~and placing of rear-view mirrors.

The conditions of greatest visual difficulty arise when vehicles meet at night, and the theoretical and experimental work which has led to the design of modern meeting beams is described. The distinctive features and performance of British, American and Continental head- lamps are discussed, as well as recent investigations on yellow light andpolarized light. The possible use in the future of polarized light and automatically aimed headlamps is considered.

Experiments to determine the best type of beam for foglamps

are described, and the reasons for the use of headlamps as warning

lights in daylight fog are given.

The desirable optical characteristics for side, rear and stop

lights and reflectors are discussed, the relevant British standards are ~

given, and recent experimental work on ways of improving the

conspicuity of flashing direction indicators is described.

Year 196Z

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• , . . . •

J E H U , V . J . D e v e l o p m e n t s in v e h i c l e and s t r e e t l i g h t i n g . Bull. Inst. Phys., Lond., .1962, 13 (I0), 269-76.

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A general review of the work done by the Road Research Laboratory

is presented in this article. The surveys of vehicle lighting indicate that the maximum glare intensity, to which opposing drivers should be exposed, should be in the range of 900-.1800 cd for low beam meeting conditions. Moreover, by applying the Stiles-Holladay law, the glare intensity of any headlamp system can be determined for a given road width and object position. The sight distances provided with the new British headlight systems are compared among themselves and the new American 4-1amp system. The author states that Visibility distances much greater than the present American and British quadro- lamp systems provide, i. e. , 63 m and 66.5 m, respectively, is unlikely with conventional headlights.

In addition, the requirements of polarized lighting as • well as the limitations of polarized light, yellow lights, and foglarnps are presented.

Finally the author discusses, often quantitatively, the factors which enter into the effective design of One overhead street lighting system. Such factors as the road surface reaction characteristics, road width, lamp distribution, light source colour, and reflectivity and skid resistance are discussed.

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Year 1963

16. DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESEARCH, ROAD RESEARCH LABORATORY. Polarized lights. Research on Road Safety. London, 1963 (H. M. Stationery Office), pp. 244- 5 i.

The principles involved in the proposed use of polarized headlight

systems and suggested methods of use are discussed in relation to the driver's own beam, depolarization on reflection, transmission and extinction coefficients, the opposing beam, sources of light leakage,

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and proposed American and German systems.

17. JEHU, V.J. How polarized headlighting might be introduced.

Lighting Problems in Highway Traffic, Proceedings of a

Symposium held at the Wenner-Gren Center, Stockholm, Sweden,

October 1962. Oxford, London, New York, Paris, 1963

(Pergamon Press), pp. 137-49; Discussion, 149-51.

The design of lower headlight beams in ordinary light has reached such

an advanced stage that further increases in seeing distance at the

meeting of similar lamps become increasingly difficult to achieve. The polarization technique applied to powerful upper headlight beams offers

a means whereby greatly improved vision during encounters can be

achieved. As the installation of a polarized light system on a vehicle

does not help the driver of the vehicle itself, but only other drivers, a

polarized system would ultimately have to be adopted by all to be of •

maximum value. The cost and the difficulties likely to be encountered

during the transition period of mixed use, however, have so far prevented the introduction of such beams.

A possible course of action which would reduce transition

difficulties would be first to introduce a polarized lower beam compatible

with normal lower beams. In the early stages of such a change, drivers

would not need to use a visor, but as more vehicles were equipped the

visor would become increasingly beneficial during meetings on both dry

and wet roads. Whether or not the absence of glare with such a system

would outweigh the disadvantages of a dimmer road surface, loss of

silhouette vision and loss of advance warning of an approaching vehicle

would need to be determined by a comprehensive driver-appreciation

test carried out in a particular locality such as an island, or perhaps in

an establishment having under its control a system of roads and a large

fleet of vehicles. For the purposes of this test the necessary equipment

could be added to existing vehicles.

Should the polarized lower beam prove to be acceptable it could be

built into new vehicles, using four headlamps; two polarized lamps

would provide the lower beam and two unpolarized lamps the upper beam.

This system could be the forerunner of the polarized upper beam, with

which it would also be compatible.

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Year 1969

18. CHRISTIE, A.W. Polarized headlights: Notes based on discussions in Stockholm in May 1969. Ministry of Transport, Road Research Laboratory Technical Note TN 409. Crowthorne, 1969 (Unpublished).

The Official Swedish Council on Road Safety Research called a Symposium on Polarized Headlights to obtain advice from other countries who have studied the problem of introducing such lighting, and to try to find a basis for co-operation in solving any remaining problems.

This Note provides information on the discussionsat the Symposium which was held in Stockholm in May 1969.

19. MOORE, R.L., and A.W. CHRISTIE. Prospects for improving vision on the roads at night. Ministry of •Transport, Road Research Laboratory Technical Note TN 440. Crowthorne, 1969 (Unpublished). •

The high accident rate at night is discussed in relation to improvements in street and vehicle lighting. It is considered that there are good prospects for improvements in street lighting, but in the field of vehicle lighting a primary obstacle is that of maintaining the correct aim of vehicle headlamps. Ways of overcoming this are discussed. The difficulties of changing to polarized light systems is referred to and this solution is regarded as a possibility in five-ten years provided certain changes in windscreen design are made.

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Year 1970

20. M O O R E , R . L . , and A . W . C H R I S T I E . P r o s p e c t s f o r i m p r o v i n g v i s i o n on t h e r o a d s at n i g h t . P o l i c e R e s e a r c h Bu l l . , 1970, (13) , 9-16.

Factors affecting visibility during dark hours is discussed in relation to improvements in street lighting and vehicle lighting. It is concluded that there is room for development in street lighting practice, and the automatic compensation of headlamp aim for changes in loading and automatic dimming of the dipped headlight intensity would greatly improve night driving conditions.

A fresh study of polarized headlights is desirable to see how earlier difficulties can now be overcome.

1. ~ • M O O R E , R . L . , ' a n d A . W . C H R I S T I E . S o m e c u r r e n t v i e w s in the . U n i t e d K i n g d o m on p r o b l e m s of n i g h t v i s i b i l i t y . . T e n t h I n t e r - ~. n a t i o n a l S t u d y W e e k in T r a f f i c and S a f e t y E n g i n e e r i n g , R o t t e r d a m , 7th - l l t h S e p t e m b e r 1970 T h e m e III. R e c e n t d e v e l o p m e n t s in m e t h o d s of i m p r o v i n g n i g h t v i s i b i l i t y - L o n d o n , 1970 ( W o r l d T o u r i n g a n d A u t o m o b i l e O r g a n i s a t i o n (OTA)) . (In t h e P r e s s ) .

The method now adopted in the United Kingdom for deciding whether or not a principal road should be lighted is outlined. The draft International Regulations for Public Lighting at present being discussed by the C.I.E. appear to the authors to involve technical procedures which although possibly correct lead to results not greatly different from those arrived at by the much simpler British Standard Code of Practice.

The interaction of street lighting and vehicle lighting is discussed and two devices which would make the use of headlights in well lighted streets visually acceptable are briefly described.

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Year 1937

3. REPORTS FROM OTHER SOURCES

i. CHUBB, L.W. Jr. Polarized light for motor vehicle lighting. Trans. illum. Engng Soc., N.Y., 1937, 3_22 (5), 505-30; Discussion 530-43.

This paper describes :a selective system of vehicle lighting using polarized light and giving ample driving light with freedom from glare. It is shown that differentiation between driving light and opposing headlights can be obtained by one of four methods of selection. The preferable method, using polarized light at 45 °, is more fully covered. PolariZed light, means for obtaining it and system of applying it to vehicle lighting are described. The adaptation to motor vehicles and a comparison with current systems of beam control are given. Safety, need for legislation and the necessary steps to adopt the system are indic at e d.

An Appendix is added to show formulae necessary for the q~antitative treatment of new factors brought into the lighting problem because of the use of~polarized light.

Year 1938

. GRABAU, M. Polarized light enters the world of everyday life.

J. appl. Phys., 1938, --9 (4), 215-25.

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Three new polarizing materials which utilize the dichroic properties

of certain crystals are described. These are Marks Plates, Zeiss

Bernotor filters and Polaroid.

Reference is made to the optical properties of Polaroid which

became commercially available in 1937, there is a classified list of

some applications of plane polarized light which includes the use of

extinction of light by "crossed" polarizers in the elimination of auto-

mobile headlight glare.

Every vehicle may have its headlamps and windshield equipped

with Polaroid screens uniformly orientated at 45 ° to the vertical. The

driver can then see ahead in the light from his own headlamps, but his

windshield will quench the direct light from the headlamps of a car

coming in the opposite direction.

Year 1939

3. GIBBS, H.T. Polarized light for motor vehicles. J. Frank.

Inst., 1939, ZZ8 (6), 719-31.

An i n v e s t i g a t i o n is d e s c r i b e d d e s i g n e d to d e t e r m i n e q u a n t i t a t i v e l y t h e e f f e c t on s e e i n g c o n d i t i o n s of c h a n g i n g t h e c a n d l e - p o w e r o v e r a w i d e r a n g e , bo th w i t h and w i t h o u t p o l a r i z a t i o n . T h e e f f e c t of c h a n g i n g t h e r e f l e c t i o n f a c t o r of t he r o a d s u r f a c e and of t h e o b j e c t w a s a l s o i n v e s t i g a t e d , and t h e r e s u l t of e q u i p p i n g p r e s e n t c a r s w i t h p o l a r i z i n g m a t e r i a l w i t h o u t i n c r e a s e in l a m p s i z e w a s c o n s i d e r e d .

Tests were made on a model road (indoors) built on a scale of

1 to Z4. Three road surfaces were used, and a black, grey or white

test object placed in one of three positions. One observer was used in

conditions of glare, no-glare, polaroid with glare and polaroid with

no-glare to provide Z000 observations in all.

17

Results indicate that:-

(1) In conditions without Polaroid it is desirable to increase the candle-power of present systems above 32.

(z) There is little, if anything, to be gained by the introduction of Polaroid with lamps of the present candle-power. There would be a definite decrease in visibility distance for white objects, which loss is diminished in the case of the grey object, and changed to a slight gain for a black object.

(3) To obtain the present no-glare visibility with Polaroid, it seems necessary to increase the source candle-power to three or four times its present ,value;

. WEIGEL, R.G., O.H. KNOLL and J. SCHIESS. The optical properties of road surfaces illuminated by ordinary and by polarized light. Das Licht, 1939, 9_(Ii), 219-23; (12), 242-5.

The conditions of vision by ordinary and by polarized light differ in two important respects: (a) for a source of given intensity the actual illumination of the road is less in the case of polarized light, owing to the absorptive action of the polarizer; (b) the reflecting powers of the surfacing differ according to the type of light used. Additional contributory factors are the effects of partial depolarization and the rotation of the plane of p.olarization. A comparative study has been made of the reflecting properties of worn road surfacings of four types (asphalt, tar, concrete and stone setts)when illuminated by ordinary and by polarized light. The apparatus employed permitted the photometric examination of specimens at any angle of incidence. In most cases the distribution of reflected light was studied on dzy surfacings for two angles of incidence and the ratio between the inten- sities of reflected ordinary and polarized light was determined for each type of surfacing. It was found that:-

(1) The difference between optical conditions on two opposing carriageways will be exaggerated by the use of polarized light.

(2) Of the surfacings examined, concrete possesses the optimum reflective properties for polarized light.

18

(3) Even with concrete the intensity of the source required for satisfactory illumination with polarized light must be about four times that required for ordinary light.

(4) Colour differentiation is improved when polarized light is used.

Year 1941

. ROPER, V., and K.D. SCOTT. Seeing with polarized headlamps. Illum. Engng, N.Y., 1941, 3__~6 (i0), 1205-13; Discussion, 1213-8.

Laboratory and •full-scale experiments have been made to determine the possibility of using polarized light in vehicle headlamps, in combination with suitable analysers in the line of vision of the drivers. The visibility attained is compared with that obtained with ordinary light, and the technical difficulties connected with the adoption of the polarized system are discussed.

Year 1945

. NELSON, J.H. The automobile headlamp: a study of the beam distributions needed for motor vehicle driving lights. Trans. illum. Engng Soc., Lond., 1945, 10(3), 49-76; Discussion, 76-81.

19

The design of motor headlamps is considered with reference to the following conditions of use: (a) driving on the open road when only one vehicle need be considered; (b) the encountering of two vehicles, both of which carry lamps; (c) driving in fog. The general theory of head- lamp beam design is briefly discussed with regard to the following facts:-

(i) The carriageway does not present a smooth horizontal surface.

(2) The apparent value of the reflection factor depends on the angle of incidence, increasing greatly at grazing incidence.

(3) In practice, the relative positions of lamp and road vary cons ide r ably.

(4) The driver is concerned with the apparent brightness of the road surface as viewed from near the lamp.

The equations developed are then used to determine the optimum horizontal and vertical distribution of light for open-road driving. A tentative specification, summarized in diagrams showing the relation- ship between candle-power and the angle between the lamp axis and the direction of the beam, is compared with the American provisional "upper beam" specification. The requirements of lamps for city driving only are specially reviewed, and a horizontal distribution diagram for these conditions is given. In the case of encountering vehicles, the effect of glare on visibility distance, and the change in this distance when a driver is facing lamps of the same candle-power as his own, are summarized graphically, the principal aspects of the problem of glare are discussed, and proposed solutions are reviewed with regard to:-

(I) The use of permanently non-dazzling lamps.

(2) The use of special lamps when encountering other vehicles.

(3) The use of polarized light.

(4) Dual carriageways.

(5) Street lighting.

A form of beam specification suitable for use on British roads is summarized graphically and compared with the American provisional "lower beam" standard and with the Dutch (1938) specification for "encountering" beams. Stress is laid on the importance of lamp setting and a portable setting device for garage use is described. The problems

20

of movement in fog are reviewed with reference to possible developments

in radiolocation and such other aids to movement as specially designed

fog lamps, and the provision of beacons at important points on the route

and of reflector signs excited by the lamps of the vehicle but acting as

self-luminous sources.

Year 1947

. LAND, E.H. The completion of the technical development stage

of the polaroid glare-eliminating system. Demonstration for

American Association of Motor Vehicle Administrators by

Engineering Liaison Committee of Automobile Manufacturers

Association, Detroit, November i0, 1947. Cambridge,

Massachusetts, 1947 (Polaroid Corporation).

Demonstration was given of a polarized system comprising a pair of

125 watt polaroid headlamps for country driving, a pair of special non-

polarizing passing lamps for city driving, and for passing old cars

during the transition period when both polaroid and sealed beam head-

lights are on the road together, and a polaroid viewer.

The polaroid system provides 122 m visibility distance with two

approaching cars 61 m apart, while at the same distance present-day

sealed beams provide a visibility distance of 53 m when on upper

beams and 61 m on lower beams. In addition, there is no blind driving

zone and pedestrians are visible at all times. No difficulty is seen in

the introduction of the polaroid system, and it is considered that the

transition from sealed beam to polaroid headlights will be far safer

than the transition between pre-sealed beam and sealed beam.

21

Year 1948

. ANON. Report on polarized headlighting. Publ. Saf., 1948, 33 (2), 12-3 .

The arguments for and against the introduction of polarized head- lighting are summarized with reference t~o papers presented at the Twenty-seventh Annual Meeting 1947 of the Highway Research Board by E.H. Land, (The polarized headlight system), J.H. Hunt, (The automobile industry survey of polarized headlighting) and V.J. Roper, (The General Electric Co. tests on polarized headlighting).

. BILLINGS, B.H. , and E.H. LAND. A comparative survey of some possible systems of polarized headlights. J. opt. Soc. Am., 1948, 38(10), 819-29.

In a polarizing headlight system polarizers are placed on automobile headlights and in a viewer before the eyes of automobile drivers. These polarizers are so orientated that the viewer is crossed with the headlights of an approaching car. This blocks most of the light from approaching headlights. A polarizing system has other features which make it different from a non-polarizing system. The amount of the polarized component of the reflected light from an object illuminated by a car's headlights which is transmitted back through the viewer in the same car depends on the type and orientation of the polarizers. Thus objects have different brightness depending on the polarizing system being used. Similarly, the contrast between objects and their background will be different for different polarizing systems. In this paper some basic matrices of an optical calculus are derived. This calculus is then used to show the orientation of the headlights and viewer polarizers for all possible polarising systems. For each of these systems the relative brightness of a specularly reflecting object is determined. Finally, equations are derived for the contrast of various types of objects with their background and a few special cases are calculated.

22

i0. HUNT, J.H. The automobile industry survey of polarized head- lighting. Bull. Highw. Res. Bd Wash., 1948, (ii), 21-9. ~ :

This paper gives a summary of the findings of a survey carried out by the Engineering Liaison Committee of the Automobile Manufacturers Association, and argues against polarized headlights: (a) only use is in rural areas and this is a small percentage of vehicle miles; (b) it requires raising and lowering of the polarized visor entering and leaving urban areas; (c) it would cost $30 - 80 per car; (d) it eliminates atmospheric glow and this makes night driving more dangerous; and (e) it would be illegal in most states under present laws and, therefore, much legislation would be required.

11. JOHNSON, Le V. Merits of polarization. Traff. Engng, 1948, 18 (4), 160-2 .

Papers presented by E.H. Land, (The polarized headlight system) J.H. Hunt, (The automobile industry survey of polarized headlighting), and V.J. Roper (The General Electric Co. tests on polarized head- lighting) at the 27th (1947) annual meeting of the Highway Research Board are discussed. These papers provided information on the whole question of theuse of polarization for the elimination of headlight glare.

12. LAND, E.H. The use of polarized headlights for safe night driving. Traff. Q., 1948,_2 (4), 330-9.

In this paper the author, who is the President and Director of Research of the Polaroid Corporation discusses the dangers of night driving, explains how polaroid headlights improve visibility, and discusses the difficulties to be faced during any transition period from conventional to polarized headlamps.

23

13. LAND, E.H. The polarized headlight system. Bull. Highw. Res. Bd Wash., 1948, (ii), 1-20.

The technical evolution of a polarized headlight system consisting of polarizing filters on two I25-watt headlamps and a viewer-filter before the driver's eyes has been completed. The polarizing direction of the viewer is parallel to his own headlights and crosses automatically with that of oncoming cars, thereby reducing the brightness of approaching headlights on the average to one-seventh of the down beam of the current Sealed Beam headlamps. The higher wattage overcomes the light loss at the polarizing filters sufficiently to make open road visibility of critical hazards seen through the viewer at least as good as present open road seeing with the upper beam.

This system has been referred by the Automobile Manufacturers Association to the American Association of Motor Vehicle Administrators for consideration. The limitations of beam control in dealing with the glare problem and the particular properties of polarizing light are cited. The period of transition to the polarized system need introduce no new hazards not found in the current transition from pre-Sealed Beam to Sealed Beam lamps. Research data from General Electric Company is presented which indicates that even misuse of the new headlamp would be no more hazardous than misuse of the Sealed Beams now.

The cost of such a system would not be out of line with the benefits obtained. The importance of public education and support of glare elimination by consumer organizations is stressed. The technical acceptability of the system has been established. The only problematical areas remaining are related to methods and results of introduction.

14. MARSH, B.W. Report of Committee on Night Visibility. Proc. Highw. Res. Bd Wash., 1948, 28, 508-13.

This report reviews research in night visibility and presents topics for further research. Mentioned are headlight dimming, use of colored glasses, yellow headlights, highway lighting, roadway delineation, and polarized headlights. Although nearly all states have statutes requiring that headlights be dimmed, a large percentage of drivers, more than 10 per cent, do not lower their lights. Tests conducted by General Electric on the use of colored glasses showed that tinted glasses gave seeing distances equal to those without glasses; however, without opposing

24

g ~ a r e t h e r e w a s a r e d u c t i o n o f s e e i n g d i s t a n c e w i t h t h e g l a s s e s . D e v e l o p e r s o f p o l a r i z e d h e a d l i g h t i n g s a y t h e i r p r o d u c t i s t e c h n i c a l l y r e a d y f o r a d o p t i o n . H o w e v e r , t h e a u t o m a n u f a c t u r e r s h a v e r e c o m m e n d - e d a g a i n s t d o i n g so , a n d p r o g r e s s i n d e c i d i n g f o r o r a g a i n s t a d o p t i o n o f p o l a r i z a t i o n h a s r e a c h e d a s t a n d s t i l l .

15. ROPER, V.J. Headlighting without glare. Proc. Inst. Traff. Engrs, 1948, 17-28.

The problem of providing safe night visibility with opposing glare present is discussed. The author presents many of the factors, such as glare sensitivity, headlight misaim and deterioration, speed of travel, driver attention, headlamp intensity, etc., which affect the problem of providing night seeing-distances which equal or exceed safe stopping distances.

Seeing-distance curves are presented for the various combinations of meeting situations involving polarized headlamps, sealed beam head- lamps, and pre-sealed beam headlamps. Information concerning a tolerable level of both discomfort and disability glare and the transition period to complete polarized headlighting is presented.

." S"

16. ROPER, V.J. The General Electric Co. tests on polarized headlighting. Bull. Hi~hw. Res. BdWash., 1948, (Ii), 30-6.

Tests are described in which six observer-drivers were used to compare visibility distances of man-sized dummies in dark clothing obtained with sealed beam headlamps and polarized headlamps. The test roadway was a stretch of straight level concrete, and the two t e s t c a r s s t a r t e d a t e a c h e n d 1 . 6 k i n a p a r t a n d t r a v e l l e d in a d j a c e n t l a n e s a t a u n i f o r m s p e e d of 64 k m / h .

25

Year 1949

17. .CHUBB, L.W. Jr. Glare and hilltop gaze. Traff. Engng, 1949, 19 (6), 267-9, 279.

A polarized viewer-headlight system, prevents a driver from seeing the atmospheric glow which is looked for by some drivers at night as a warning of the approach of other vehicles at or near hilltops, curves or depressions in the roadway, various ways of overcoming this dis- advantage is discussed, and it is suggested that a strip of bi-refringent material such as cellophane or polyvinyl alcohol plastic sheeting, suitably orientated, could be incorporated in the viewer.

18. R O P E R , V . J . M i n i m u m g l a r e . T ra f f . Engng, 1949, 1__29 (4), 151-7.

The results are presented of tests to compare the visibility distances when sealed-beam, and polarized systems of headlighting are used.

Year 1950

19.

Z6

A U T O M O B I L E MANUFACTURERS ASSOCIATION, ENGINEERING LIAISON C O M M I T T E E . A g a i n s t the adopt ion of p o l a r i z e d h e a d - l i gh t s a t t h i s t i m e . T ra f f . Engng, 1950, 21 (1), 16-9.

The pros and cons of polarized headlighting are discussed. Full scale tests were conducted.using 125 watt polarized headlamps and polarxzed visors supported from the windshield frame. The cars were also equipped with city lamps, for in city streets the visors could not be used as they absorbed over 60 per cent of the light provided by .street. lighting, Strains in.the windshield were a problem, an,increase in electricity requirements was necessary and there was an increase in weight due to the new components. The cost of introducing the change is estimated to be between ~3,0. 00 to S80..00~per ear. i

20. CHUBB, L.W. Jr. Polarized light for auto headlights. Traff. En,gng, 1950, 20 (7), 265-7.

This article discusses those fundamentals of polarization which are of particular importance in the head.lighting" application.

21. LAND, E.H. , and L.W. CHUBB. Polarized light for auto head- lights. Traff. Engng, 1950, 20 (i0), 384-6, 399.

The sealed beam lighting system is described, its disadvantages examined and the advantages offered by a suitable polarized light system explained. The practical difficulties involved in the introduction of polarized headlamps are discussed and suggestions are made for overcoming these.

Year 1.951

22. ANON. Polarized lights on highways. Engng News - Rec. , 1951, 146 (I0), 21.

27

Legislation designed to advance the day when polarized headlights may be required on all motor vehicles on highways has been introduced into the legislative chambers of Massachusetts and New York, according to a bulletin of the National Highway Users Conference. Thebill in Massachusetts would require a polarized viewer, two polarized head- lamps and two non-polarized passing lamps on all cars manufactured after a specified date, but only if States with an aggregate population of 50 000 000 people adopt similar legislation. In New York's bill~ this equipment would be required after January i, 1954.

23. HAVENS, J.H., and A. C. PEED Jr. Field and laboratory evaluation of roadside sign surfacing materials. Bull. Highw. Res. Bd Wash., 1951, (43), 32-44.

Physical and optical characteristics of sign materials and design and application of a reflectometer devised by the Kentucky Department of Highways are discussed. Accelerated weathering procedures and specification standards are described.

Field studies paralleling laboratory work and a possible correlation between the two are described. The field work included several thousand individual observations covering 30 different sign- surface types under actual conditions on a night-visibility driving- course. Most of the major types of surfaces available were represented.

In addition to using ordinary sealed beam headlamps, field observations were made using polarized headlamps and viewers.

Year 1952

24.

28

ALLGEMEINER DEUTSCHER AUTOMOBIL-CLUB. (i) Comparative tests using the standard double-filament type headlight system and a polarization-type headlight system.

(Z) ADAC tests with a polarized headlight system - "Pola" anti-

dazzle system. Munchen, 1952 (Allgemeiner Deutscher

Automobil-Club e. V. )

D y n a m i c a n d s t a t i c t e s t s o f t h e r e l a t i v e m e r i t s o f t h e t w o s y s t e m s a r e

d e s c r i b e d . A b o u t 1Z c a r s a n d t w o m o t o r c y c l e s t o o k p a r t i n t h e t e s t s

w h i c h t o o k p l a c e on a 2 k m s t r e t c h of c o n c r e t e r o a d 8 t o l 0 m i n w i d t h .

Bilux is the normal headlighting system used in Germany. On

cars the two headlamps provide both the open road beam and a

horizontally cut-off meeting beam. Motor cycles have one similar

lamp.

The "Pola" polarized meeting beam was produced by two

additional headlamps each of 50 watt designed to restrict the light

intensity near the horizontal to 625 cd per lamp. Motor cycles had a

Z5 w bulb. The polarizing material is Polarex, a German product

sandwiched between glass plates. The analyser or viewer takes the

form of a visor or half spectacle. Test runs were made with Bilux v

Bilux and Pola v Pola.

R e s u l t s i n d i c a t e d t h a t v i s i b i l i t y d i s t a n c e s o b t a i n e d w i t h t h e P o l a

s y s t e m w e r e g r e a t e r t h a n w i t h t h e B i l u x s y s t e m , 100 m a s a g a i n s t

65 m in t h e o p e n r o a d s i t u a t i o n , a n d 60 m a s a g a i n s t 28 m i n t h e d a z z l e

s i t u a t i o n . T h e s y s t e m is a l s o c o n s i d e r e d s u i t a b l e f o r m o t o r c y c l e s .

25. AUTOMOBILE MANUFACTURERS ASSOCIATION. The public side of the problem of polarized automobile lights. A

~50 000 000 question in Massachusetts with a i- to -30 chance of

benefit to the car owner. Detroit, Michigan, 1952 (Automobile

Manufacturer s As s ociation).

Polarized headlights give glare relief only if conditions are exactly

right, but not in city driving, when cars meet at angles or on sharp

curves, when they overtake one another, or in "mixed" meetings with vehicles using regular headlamps.

Mixed use of these lights and conventional automobile headlights

would create unusual hazards on the highways for many years.

Z9

The polarized lights are not a "cure-all" for night driving and

seeing problems. Actually they are so bright that they cannot be used

at all in congested areas or for city driving. The visors or goggles

used with the system would be unsafe to use in cities at night because

they reduce street lighting effectiveness 60 per cent.

Pedestrians and others near highways would be "glared" and

inconvenienced by these new, brighter lights.

Individual installations on existing automobiles would cost up to

~200 each. The proposed system of introduction by a Massachusetts law would hamper interstate travel. In a five year period (based on

1946 to 1951 experience) it would cost Massachusetts owners of new

automobiles ~50 000 000, and they would end up with only one chance

out of 32 to use the system in meeting a line of oncoming cars on the

highway.

Because of urban development there would be less chance to use

these lights in Massachusetts than in most other states. As to the

possibility of reducing night accidents, only 56 out of 488 fatal

accidents in 1950 (a typical year) occurred at night on rural highways.

26. WEIGEL, R.G. Protection from'glare bythe use of polarized

light. Zichttenchnik, Wien, 1952, 4 (5), 129-32. (In German).

Glare experiments are described in which an "observer vehicle" was

driven at 70 km/h towards a "dazzle Vehicle" in an experimental

street five metres wide. Two targets 0.35 ruby 0.40 m, and one

target 0. Z m 2 with reflectance factors of either five per cent or 40" per

cent were raised as required from slots in the ground within a distance

of 75 m in front of the observer vehicle. The time taken by the

observer to perceive the target (perception time) was used as a

measure of dazzle. The results indicated that the application of polarized light is able to offer an effective protection from glare.

Reference is made to light losses in the polarizers, trans-

mission and extinction coefficients, and the reflection properties of

road surfaces in polarized light.

30

Year 1953

27. ALLGEMEINER DEUTSCHER AUTOMOBIL-CLUB. Has the

dazzle problem been solved? Int. Rd Saf. Traff. Rev., 1953,

! ( 1 ) , 5 - 1 0 .

The "Pola" anti-dazzle system is described. It is claimed that:-

i. The system of polarized passing-lights would make possible a

considerable increase in seeing distance, as dazzle would be

eliminated and a better distribution of light obtained.

. T h e s y s t e m c o u l d b e i n t r o d u c e d , w i t h o u t h i n d e r i n g o t h e r r o a d - u s e r s , w h i l e the " B i l u x " ( o r d i n a r y d i p p e d h e a d l i g h t s ) s y s t e m is s t i l l in u s e on the s a m e r o a d s . T h e d r i v e r w h o h a s a d o p t e d t h e n e w s y s t e m w i l l p r o f i t f r o m i ts a d v a n t a g e s .

. The n e w s y s t e m d o e s n o t r e q u i r e m o r e p o w e r f u l b u l b s . I t w o u l d t h e r e f o r e b e p o s s i b l e to u s e it on v e h i c l e s w i t h g e n e r a t o r s o f limited capacity. Where the generator is of sufficient capacity,

more powerful bulbs could be used without hindering other road

u s e r s .

It is considered that the full effect of polarized passing-lights will be

seen when all or nearly all motor vehicles are equipped with the new

system. This can be achieved only through universal adoption of this

new system.

28. HELLWIG, H, W. Motor vehicle headlights for the selected use

of natural and polarized light. Westf~ilische Metall - Industrie

G. m. b.H. Lippstadt, 1953 (Westf~[lische Metall - Industrie

G.m.b.H.)

Technical details are given of the headlamps which comprise two

axially divided reflector halves, one of which is equipped with a semi -•

circular polaroid filter. Thus half of the reflector transmits polarized

light either as a full beam or a dipped beam depending on the adjustment

of the helix in the focal point, and the other half produces the normal

full beam and dipped beam. 31

Year 1954

zg. JOSEPH LUCAS LTD. The use of polarized light for the

prevention Of dazzle from motor car headlamps. Joseph Lucas

Research Laboratories Report No. L. 1903. Birmingham, 1954"~

(Joseph Lucas Research Laboratories).

It is apparent that while Polaroid offers an ideal solution to the dazzle

problem, there remains a number of major problems to be solved

before universal application could be recommended. The material

available at present would cause a loss of light amounting to more than

four-fifths of that available, and this could only be compensated for either by a redesign of the electrical equipment or by the introduction

of a new kind of polarizing material. The critical setting of the

analyser would prove a disadvantage, if this were not alleviated by the

use of suitable screens to turn the plane polarized into circularly polarized light. The stressed skin type of safety glass seems to

present the most serious difficulty to the use of polarized light. The

use of the laminated windscreen would be the most desirable solution,

and would be far better than using external visors. The incorporation

of the analyser in the windscreen as a laminated sheet is not advisable

as there are occasions when this would cause a serious loss of

visibility.

30. ROPER, V.J. Seeing withheadlamps. Rd Int., 1954, (12), 15-8,

62.

The author describes tests with observer-drivers to determine how far

a person can see with headlights, both on the open road with no approaching headlights and when facing the glare of opposing headlamps.

Some of these tests were made with drivers who did not know they were

engaged in seeing distance tests, and these drivers saw the obstacles

only half as far away as drivers who knew they were engaged in a test.

Comparisons are given of seeing distance values as a driver approaches

and proceeds beyond another single vehicle - with present sealed beam

headlights properly used and with experimental 125 watt polarized

headlamps. The seeing distance remains reasonably constant with

32

polarized headlighting - as contrasted to considerable variation in seeing distance with ordinary light.

Year 1957

31. MAKSH, C. Highway visibility in fog. Illum. Engng, N. Y., 1957, 52 (IZ), 6Zi-8.

This paper is a progress report of investigations at the Pennsylvania State University, and deals with the problem of fog on turnpikes. A polarized spot lamp (i00 watt) and cross polarized viewer was found to be the most effective fog lamp system developed so far, although polarized light penetrates fog to no greater extent than unpolarized light. Polarized light which is scattered back from fog is not de- polarized but is blocked when seen through a viewing filter polarized at 90 ° to the lamp filter, thus removing much of the veiling glare normally present. Light striking opaque objects lacking metallic lustre is partially depolarized and the objects therefore can be seen through the filter. Self luminous objects, such as tail and signal lights, and traffic signals, as well as opaque objects, are not obscured by the filter. Restrictions to be observed for the satisfactory performance of a polarized fog light system are given.

33

Year 1958

32. MEESE, G.E. Engineering headlights for safer driving. Gen. Elect. Rev., 1958, (Sept.), 18-21.

This article discusses the problem of providing adequate seeing distance with minimum glare to opposing drivers. The primary advances in the design of the lower beam are mentioned. The visibility criterion used in design involved limiting the light reaching the eyes of the opposing driver to not greater than I000 candle-power per lamp. This limit will provide a minimum of visual interference and an acceptable level of comfort for the opposing driver. To meet this criterion, the lower beam should have a minimum amount of light in the upper left quadrant of the visual field and as much light as possible in the upper left corner of the lower right hand quadrant.

From an optical standpoint, the most successful headlight system contains a parabolic reflector with a small light source. The author mentions the development of a mechanical device used to aim the new non-symmetrical dual headlights. The current trend in headlight systems of separating high and low beams into separate lamps is described. This separation of beams may improve a driver's margin of safety in night vehicle encounters.

The article concludes with a discussion of the reasons for the failure of polarization to provide the solution to the night visibility problem. The major disadvantage of polarized headlights appears to be its incompatibility with existing systems, which would cause visibility loss to be great for drivers not wearing properly polarized glas s es.

34

Year 1959

33. CHERNYSHEV, B. , and A. SHALATOV. The problem of dazzle caused by vehicle lights. Avtom. Transp., 1959, 37 (7), 45-7. (In Russian).

A review is presented of methods which have been proposed to reduce or combat dazzle caused by vehicle lights. The advantages and dis- advantages are discussed of the following: (I) dipping lights, (Z) the asymmetric beam system incorporated in the Chaika and Moskvich cars, (3) the metal disc shield inserted in headlamps, (4) polarized glass for headlamps and windscreens, (5) yellow paint for the upper half of head- lamp glass, (6) an additional side light with rear and side beam, (7) a semi-transparent shield for the driver which can be lowered to eye level, (8) illumination of the vehicle interior with pale green light. Recommendations are made for the regular and effective testing of vehicle lights, the improvement of road lighting and the planting of more hedges on the central reserve of dual-carriageway roads.

Year 1962

34. LINDAE, G. Vehicle lighting - a contribution to safety. Auto- tech. Z., 1962, 64 (5), 152-8. (In German, with English summary).

Present vehicle headlight designs in the U.S.A. and in Europe are compared, especially with regard to the light distribution and visibility distance obtained with dipped headlights. Various alternatives for increasing visibility distance and reducing glare are reviewed,

35

including polarized light, improvements in the adjustment, improving the design of the cover plate which produces dipped headlights (so- called M-headlights), and the use of bulbs filled with wolfram-iodine vapour. Glare from vehicle signal lights is also discussed.

Year1963

35. INGELSTAM, E. (Editor). Lighting problems in highway traffic. Wenner-Gren Center International Symposium Series, Vol. 2. Oxford, London, New York, Paris, 1963 (Pergamon Press).

This volume contains papers presented at a symposium held in Stockholm in 1962 and organized by the Swedish Council of Road Safety Research. Subjects covered include glare effect from the stand- point of physiological optics, research and visual problems in night driving, adaptation time after glare, and how polarized headlighting might be introduced.

36. INGELSTAM, E., and B. KJELLBERG. Problems and some findings with polarized headlights. Lighting Problems in Highway Traffic, Proceedings of a Symposium held at the Wenner-Gren Center, Stockholm, Sweden, October 1962. Oxford, London, New York, Paris, 1963 (Pergamon Press), pp. IZI-35.

Tests carried out in Sweden to gain practical information on polarized light are described. Conventional lamps produced three times as much light at a quarter of the wattage of polarized lamps. Most drivers find polarized light better under meeting conditions than the light from a

36

n o r m a l s y m m e t r i c a l l o w e r b e a m . H o w e v e r , i t i s c o n c l u d e d t h a t t h e r e is no r e a l i s t i c r e a s o n f o r c h a n g i n g f r o m the c o n v e n t i o n a l to t h e p o l a r i z e d s y s t e m . T h e n e e d f o r i m p r o v i n g t h e p o l a r i z e d s y s t e m is s t r e s s e d .

Year 1965

37. YAMAGUTI, T. Non-glare headlight with a sodium nitrate

polarizer as a filter. J. College Arts Sciences, Chiba Uni.,

Japan, 1965, 4(3), 245-51. Japanese J. Appl. Phys, 1965,

_4 (iz), 9v3-6.

With a view of obtaining a polarization headlight which is sufficiently

bright for a free field driving and at the same time is dim to a driver of an oncoming vehicle who views the headlight through an analyser ..

placed in the crossed position to the polarizer over this headlight, a

set of polarization headlight system is constructed. It consists of a

sealed beam headlamp with a smooth front cover glass, having the same 50 watt filament as the conventional sealed beam one, a

cylindrical lens system over a part of the aperture and the sodium

nitrate polarization plate. Illuminance of this set satisfies the

Japanese Industr'ial Standard (JIS) which is equivalent to the SAE in

America, for the upper beam test points. Its maximum light intensity,

26 200 cd is about 2.7 times as high as that of the known polarization

headlight (9 800 cd) with the use of "Dichrom" or "Polaroid", and is

about 86 per cent of 30 600 cd of the conventional sealed beam head-

light.

37

Year 1966

38. W E B S T E R , L . A . , and F . R . YEATMAN. An i n v e s t i g a t i o n of h e a d l i g h t g l a r e as r e l a t e d to l a t e r a l s e p a r a t i o n of v e h i c l e s . U n i v e r s i t y of I l l i no i s , C o l l e g e of E n g i n e e r i n g , E n g i n e e r i n g E x p e r i m e n t S ta t ion , B u l l e t i n 496, Urgana , I l l i no i s , 1966 ( U n i v e r s i t y of I l l i no i s ) .

The headlight glare project was initiated in the fall of 1964 to study the tolerable levels of headlight glare as related to median performance. This report, which covers the work of the project, begins (Part i) with a discussion of the current status of knowledge of headlight glare. The factors influencing the amount and effects of glare, the suggested methods of alleviating glare, and the sources of experimental error are included.

Actual field testing was conducted in two phases: (i) disability glare, which affects seeing distance and (Z) discomfort glare, which is a psychological phenomenon. The disability glare tests (discussed in Part II of this report) involved obtaining seeing distance for ten subjects, eight targets, two beam configurations and four lateral separations (1.8, i0, 22 and 28.6 m). Data were also collected for polarized headlighting at the I. 8 m lateral separation. Conclusions as to the optimum lateral 'separation for providing seeing distances equal to or in excess of the safe stopping sight distance for 112 km/h are made, as well as statements showing the advantages of polarized head- lighting for the I. 8 m lateral separation.

Sta t ic and d y n a m i c t e s t s w e r e conduc ted on d i s c o m f o r t g l a r e . The s t a t i c t e s t s ( d i s c u s s e d in P a r t III of this r e p o r t ) p r o d u c e d BCD ( b o r d e r l i n e b e t w e e n c o m f o r t and d i s c o m f o r t ) va lues for t en s u b j e c t s , e igh t l o n g i t u d i n a l d i s t a n c e s , two b e a m c o n f i g u r a t i o n s and four l a t e r a l s e p a r a t i o n s (1 .8 , 10, 18.3 and 28 .6 m).

C o n c l u s i o n s w e r e d r a w n r e g a r d i n g the l a t e r a l s e p a r a t i o n n e e d e d to r e d u c e the d i s c o m f o r t of o n c o m i n g h e a d l i g h t g l a r e .

This r e p o r t conclfldes (Part IV) with specific s t a t e m e n t s regarding the lateral separation which produced tolerable levels of disability and discomfort glare. Also included are discussions which evaluate the research and suggest the direction of future study.

38

Year 1968

39. ERIIfSSON, B. Studies on polarizing filters and light-sources for polarized headlight system s . ~ Institute of Optical Research Report TR 17.6. 1968. Stockholm, 1968~ (Institute of Optical Research).

Measurements have been made with a view to developing a practical polarized headlight system. These comprise data for both commercial linear polarizers and specially manufactured types, including typical spectrographic transmission data for single and double polarizing sheets with varying relative orientation of the polarization axes, production variations in transmission and in orientation of the polarizing axis, heat properties, and resistance to moisture and mechanical mis- treatment. It is shown that transmission and extinction values vary considerably even over fairly small polarizing sheets and that the variations in polarizing axis orientation are small. Thermal properties vary between different types of polarizers. While 96°C breaks down some polarizers in less than 100 hours, other types endure higher temperatures (up to 120°C). Most commercial types show unsatisfactory moisture resistance and some are also sensitive to mechanical mis- treatment. Measurements on commercial and modified-commercial long-range headlamps with halogen bulbs, rated at 55, I00 and~ 150 watts, indicate the possibility of providing headlamps for a polarized system.

40. FISHER, A.J. A review of vehicle headlighting practice. University of New South Wales, Institute of Highway and Traffic Research, Human Factors Group Report No. 16, Kensington, N.S.W., 1968 (University of New South Wales).

This review.is in seven parts. In the par.t entitled "The.impr.ovement of headlamp performance!', the author Considers that recent changes in headlamp design.have not produced-significant gains in seeing distance when lamps are compared strictly on the same basis. By considering the basic geometry of a meeting situation and data relating seeing distance with lighting parameters it can be shown that no

39

significant gains .must. be expected even if there are radical increases in light in the beam. There is on the other hand, a danger of aggravating the discomfort of night driving. Nonetheless, the search goes on, using conventional means, of improving seeing especially on roads of the expressway type and a six headlamp system has been

suggested.

Modifications to vehicle and highway construction plus the improvement of the reflecting properties of objects would make night driving easier. However, large increases of seeing distance, CoOupled with the solving of problems of lamp aiming, glare from streams of vehicles and from wet roads, can be obtained using polarized lighting. The problems of introduction, however, are great.

41. HEMION, R.H. The effect of headlight glare on vehicle control and detection of highway vision targets. South West Research Institute, Department of Automotive Research, Report No. AR-640. San Antonio, Texas, 1968 (South West Research Institute).

Typical night vehicle meeting engagements on unlighted two, three and four lane highways were simulated. Vision tasks for subject drivers were provided utilizing common highway visual objects as targets. Various vehicle headlight systems including standard low and high beam, high-intensity and polarized lamps were studied under varied conditions of vehicle speed and separation distances between opposing single and multiple vehicles with respect to the vision targets with drivers having varied glare adaption response. Measurements were made of detection distance capabilities of the observers and their steering response to targets and oncoming glare vehicles.

42. HEMION, R.H. Disability glare effects during a transition ~to polarized vehicle headlights. South West Research Institute, Department of Automotive Research, Report No. AR-67Z. San Antonio, Texas, 1968 (South West Research Institute).

40

From prior studies, it was concluded that headlight glare could be

eliminated on the highway by the use of polarized headlights, but a

considerable period of time would elapse before all vehicles on the

highway could be adapted to this system. This work is a study of the

glare conditions resulting from the meetings of various combinations and configurations of polarized and unpolarized headlights which could

be encountered during the transition period to complete polarization.

In only one instance, a transient situation which need not be maintained,

would visibility be les s than that encountered with present standard low-beam headlights.

43. JOI-IANSSON, G. , and K. RUMAR. A new system for polarized

headlights. University of Uppsala, Department of Psychology,

Report No. 64. Uppsala, Sweden, 1968 (University of Uppsala).

The principles involved and experimental evidence for apolarized

meeting beam are described. The basic idea is that each car would be

fitted with the following additional equipment at an estimated production

run cost of ZOO - 400 Sw. Cr. (£10 - £Z0):-

(i) Two halogen headlamps (total at least I00 w giving at

least i00 000 cd) with built in polarizing filters.

(2) A polarized visor mounted like an ordinary sun visor which

could be lowered or raised manually or automatically into the driver's visual field.

(3) A relay and switch.

The polarized meeting beam is intended for use in rural areas only,

i.e. areas without street lighting. A polarized filter with 38 per cent

transmission, Polaroid Corporation type HN38 is considered suitable.

Preliminary experiments indicate that it is possible to use many types

of present day toughened glass windscreens, and that visibility distances

in the dark can be increased from 30 - 50 m for normal headlights to

90 to 180 m for polarized lights.

41

Year 1969

44. ANON. To see or not to see. Now, Sweden, 1969, (March) 34-5.

Research at Uppsala University in conjunction with The Royal Institute of Technology in Stockholm into polarized vehicle lighting is briefly described. Visibility experiments showed that the use of polarized lighting increased the visible distance at meetings in the dark from 30-50 m for normal headlights to 90-180 m for polarized lights. It is suggested that a method of introducing polarized vehicle lighting would be for vehicles to be equipped with a polarized visor mounted like an ordinary sun visor which could be lowered or raised manually, or installed so as to function automatically in co-ordination with polarized headlights installed in addition to normal headlights. When a "polarized" car meets another car, the driver dips his lights, in which case normal headlights are turned off, polarized meeting lights take over and the polarized visor is moved into his visual field.

45. ERIKSSON, Polarizer. Stockholm,

B. Thermal breakdown of the Polaroid HN 38 Institute of Optical Research Report TR Z0.5. 1969. 1969 (Institute of Optical Research).

This is an appendix to "Studies on polarizing filters and light-sources for polarized headlight systems" by the same author, and describes investigations into how pplarized filters are affected by repeated short periods of high temperature. The temperatures considered were 120°C and Z0°C although 95°C is thought to be the highest temperature one has to be prepared for. The filters will last at least three times longer if heated for short periods than if heated continuously.

42

46. ERIKSSON, B. Depolarization in windshields. A preliminary

report. Institute of Optical Research Report 21.5.69.

Stockholm, 1969 (Institute of Optical Research).

Windshields as fitted to a number of popular cars were measured with

regard to depolarization by placing them between a light source and a

photo-conductive cell. A polarizer was placed in front of the light-

source and an analyser in front of the photocell with its axis perpen-

dicular to that of the polarizers. Depolarization, per Cent of intensity

obtained with parallel polarizers, mean values for each sample type

varied between 2.60 for a Saab 96 to 10. 02 for a Peugeot 404 with a

~oughened windshield. The value was 5. 30 for a Peugot 404 with a laminated windshield.

47. JOHANSSON, G., K. RUMAR, J.B. FORSGREN and M. SNOBORGS. Summaries of methods and results with a new system of polarized headlights. University of Uppsala, Department of Psychology, Report for the First International Symposium on Polarized Head- lights, May 2Z-Z3, Stockholm, Sweden. Uppsala, Sweden 1969 (University of Uppsala).

Four to six subjects were tested by two methods and comparisons made

of the results both between the subjects and between the two methods.

In the field method the subjects were driven towards a stationary

car, and were required to detect obstacles covered with dark grey cloth (reflection factor five per cent).

Because some variables (e.g. angle between polarizing areas of

opposing filters) are difficult to control in field experiments, further tests were conducted in a simulator.

Consideration was given to different types of filter (the best was

found to be Polaroid Corporation HN 38), atmospheric conditions,

windscreens both laminated and toughened, effect of dirt on headlamp,

mixed systems, two wheelers, obstacle reflectance and retro reflective

material, silhouette effects in clear atmosphere, fog and snow, meeting

situations on a curved road and filter temperature within the headlamp.

43

48. JOHANSSON, G., K. RUMAR, J.B. FORSGREN and M. SNOBORGS. Experimental studies of polarized meeting light. I. Visibility distance as a function of type of polarization filter. University of Uppsala, Department of Psychology, Report No. $37. Uppsala, Sweden, 1969 (University of Uppsala). (In Swedish, with English

summary).

This report is the first o n e in a series describing experiments •with polarized headlights. The purpose is to try to find the polarization filter that gives the longest visibility distances in order to use that filter in the following experiments.

Five experiments are reported. The first two are primarily used to validate a specially built simulator. It is shown that the rank order obtained between the filters in a field experiment is also obtained in a corresponding simulator test. After that various polarization filters are tested in the simulator. Headlight intensity and angle between polarization axes of the opposing filters are varied.

The rank order between the filters was constant over the tested intensity interval (Z5 000 - 800 000 cd) and over the tried angles between polarization axes (89 ° - 83o).

The best filter was Polaroid Corporation HN 38 followed by I-IN 32, HN 42, EO 4, EO 2 (Erik Olsson), Mark's DT, HN Z2, KN 36, GH and DE (Erik Olsson).

49. JOHANSSON, O., K. RUMAR, J.B. FORSGREN and M. SNOBORGS. Experimental studies of polarized meeting light. If. Visibility distance as a function of headlight intensity under various atmospheric conditions. University of Uppsala, Department of Psycholo@y, Report S38. Uppsala, Sweden, 1969 (University of Uppsala). (In Swedish, with English summary).

Polarization of the headlight reduces its luminous output by around 60 per cent. The visor reduces the remaining reflected light by another 40 per cent, so that the effective light is only Z0-Z5 per cent of the initial output. From this it follows that the effect of an increase in light intensity will be of great interest.

44

The purpose of this investigation has been to establish how

visibility distance varies with headlight intensity, with and without an equally equipped opposing car.

The investigations were made as field experiments with a semidynamic method, which was worked out at the Institute of Optical Research in earlier experiments.

Variation of headlight intensity was made by using various numbers of headlights and in some cases by using neutral filters.

A secondary purpose has been to study the effect of various atmospheric conditions.

The results were in short:

(i) Conditions with a single car.

(a) With both polarized and unpolarized light the visibility distance is a negatively accelerated function of headlight intensity.

(b) Polarized light gives about 20 per cent longer visibility distance than unpolarized.

(c) Clear atmosphere gives about 15 per cent better results than slight haze.

(2) Conditions with an equally equipped opposing car.

(a) Under meeting conditions in polarized light visibility distance increases as a linear function of headlight intensity under conditions with clear atmosphere and slight haze, but it is nearly constant under rain.

(b) Under meeting conditions in unpolarized high- beam the visibility distance is almost constant over all headlight intensities.

(c) Clear atmosphere gives about 20 per cent longer visibility distance than slight haze, which gives 30-50 per cent longer visibility distance than rain conditions - depending on headlight intensity.

45

50 . JOHANSSON, G., K. R U M A R , J . B . F O R S G R E N and M. SNOBORGS. E x p e r i m e n t a l s t u d i e s of p o l a r i z e d m e e t i n g l ight . III. V i s i b i l i t y d i s t a n c e as a f u n c t i o n of t ype of v i s o r . U n i v e r s i t y of U p p s a l a , D e p a r t m e n t of P s y c h o l o g y , R e p o r t No. $39. Uppsa l a , Sweden , 1969 ( U n i v e r s i t y of U p p s a l a ) . (In Swed i sh , wi th E n g l i s h s u m m a r y )

ins ide - out s ide, fixed- movabl e, Various types of visors are discussed: " " z " m a n u a l - a u t o m a t i c , c a r m o u n t e d - v i s o r g l a s s e s . An o u t s i d e - v i s o r shou ld r a d i c a l l y s o l v e the w i n d s h i e l d - d e p o l a r i z a t i o n p r o b l e m . Movab le t y p e s offer better visibility under non-meeting conditions, in stree-lighted areas and in dawn and dusk. Visorglasses (of a special half-type) are a simple and unexpensive way of getting a movable visor with nearly automatic glare-minimizing adjustment.

One field experiment is reported where visibility distances for: (I) Fixed outside visor, (2) Fixed inside visor and (3) Visorglasses are compared under different headlight intensities in a symmetric meeting situation.

Fixed outside visor offered, of course, the longest visibility distances (at 200 000 cd ~-20 per cent and at 800 000 cd~ 30 per cent longer than with the two other visor arrangements) and the gain due to increased headlight intensity was larger (because of windshield depolarization was eliminated and thus less glare). Visorglasses turned out to give slightly longer visibility distances than fixed inside visor, an effect of the minimized glare due to slight headmovements (always perpendicular polarizing axes).

51. JOHANSSON, G., K. RUMAR, J.B. FORSGREN and M. SNOBORGS. Experimental studies of polarized meeting light. IV. Visibility distance under car meeting car situations between conventional low beam and polarized meeting beam. University of Uppsala, Department of Psychology, Report No. $40. Uppsala, Sweden, 1969 (University of Uppsala). (In Swedish, with English summary).

A series of measurements under car meeting car situations have been carried out with the purpose of investigating the visibility distances to be obtained with both Continental European low beam and polarized meeting beam.

46

Drivers of cars with low beam and visor shorten their visibility distance by about 5 per cent when meeting a polarized beam as compared to low beam (without visor).

Drivers of cars with polarized beam get similar visibility distances when meeting a low beam (without visor) as when meeting polarized beam (with visor).

Drivers of cars with low beam, who inadequately use their visor when meeting low beam reduce their visibility distance by about i0 per cent as compared to the same situation without visor.

The results support the proposals made in the system report (Johansson, Rumar 1968) to

introduce the polarized meeting beam gradually

use the polarized meeting beam when meeting another car independent of which lighting system this car is equipped with.

Since some of the problems associated with approaching traffic still remain unsolved this topic will also be treated in later reports.

Year 1970

52. JOH_kNSSON, G., and K. RUMAR. A new polarized headlight system. Ltg Res. Tech., 1970, 2 (1), 28-32.

The authors, who are with the Department of Psychology, University of Uppsala, Sweden, discuss the basis of a polarized headlight system proposed for introduction in Sweden. Earlier work is reviewed briefly. Proposals for introducing the system are given and related to the

47

relevant experimental studies. The equipment needed and its use in

various traffic situations are described. Methods for overcoming

problems inevitable in the transition period are outlined and the further

researches necessary are listed.

. SOME MENTIONS OF POLARIZED LIGHT

OTHER THAN AT RRL

Year 1931

BRITISH P A T E N T O F F I C E . A n t i - d a z z l e a p p a r a t u s . B r i t i s h P a t e n t S p e c i f i c a t i o n 365507. London , i931 (The P a t e n t Off ice) .

Year 1937

G A M B L E . A. La l u m i ~ r e P o l a r i s 6 e son e m p l o i d a n s l e s P r o j e c t e u r s D ' A u t o m o b i l e s . Bull . Soc. f r . E l e c t n s , 1937, 7, 511.

GRABAU, M. The optical properties of polaroid for visible lights. J. opt. Soc. A m . , 1937, 2__ ! (12), 420-4 .

KENT, C . V . , and J . LAWSON. P h o t o e l e c t r i c m e t h o d for d e t e r m i n a t i o n of p a r a m e t e r s of e l l i p t i c a l l y p o l a r i z e d l ight . J. opt. Soc. Am. , 1937, 27, 116-9.

48

LAND, E.H. Polaroid and the headlight problem. J. Franklin Inst., 1937, 224, 269.

MINDLIN, R.D. Analysis of doubly refacting materials with circularly and elliptically polarized light. J. opt. Soc. Am. , 1937, 27 (8), 288-91.

Year 1938

SAUER, H. Polarisiertes Licht in der Kraftfahrzeug-Beleuchtung, V.D.I. Zeit., 1938, 8__22, 201.

Y e a r 1940

LAND, E.H. Polarized light in the transportation industries. The Michigan-Life Conference on New Technologies in Transportation. University of Michigan Official Publications, 1940, 42, 151.

49

Year 1945

O'GORMAN, M. The problem of dazzle : the polarized light solution considered. Highws, Bridges Aerodr., 1945, II(561), i, 4.

POLAROID CORPORATION. Polarized light and its application. Cambridge, Massachusetts, 1945 (Polaroid Corporation).

Year 1948

SCHRODER, H. Production of plane polarized light by thin dielectric layers. Optik, Stuttgart, 1948, 3 (5/6), 498-53.

Year 1949

ANON. Polarized headlights. Engineering, Lond., 1949, 168 (4360), 184-5.

50

ANON. The nature of adhesion. Some results of the initial stage of U.S. Research. The Chemical Age, 1949, (May 21).

RICHARTZ, M. Analysis of elliptical polarization. J. opt. Soc. Am. , 1949, 39(2), 136-57.

WEIGEL, R.G. Die Anwendung polarisierten Lichtes zur Verhinderung der Blendung im Kraftverkehr. Optik, 1949, 5 (3). (Paganation not known).

Year 1951

BILLINGS, B.H. A monochromatic depolarizer. Symposium on Polarization, March i, 1951 Meeting of the Optical Society of America, Washington, D.C. Paper 3. J. opt. Soc. Am., 1951, 41 (12), 966-75.

BRODE, W. IZ. Optical rotation of polarized light by chemical compounds. Symposium on Polarization, March I, 1951 Meeting of the Optical Society of America, Washington, D.C. Paper 6. J. opt. Soc. Am., 1951, 4_!1 (12), 987-96.

CLAI~K JONES, R. , and C.D. WEST. On the properties of polarization elements as used in optical instruments. II Sinusoidal modulation. Symposium on Polarization, March i, 1951 Meeting of the Optical Society of America, Washington, D.C. Paper 5, J. opt. Soc. Am., 1951, 41 (iZ), 982-6.

FALKOFF, D.L., and J.E. MACDONALD. On the Stokes parameters for polarized radiation. Notre Dame, Indiana, 1951 (University of Notre Dame).

51

HALL, J.S. Some polarization measurements in astronomy. Symposium on Polarization, March i, 1951 Meeting of the Optical Society of America, Washington, D.C. Paper 2. J. opt. Soc. Am.,

1951, 41 (iZ), 963-6.

KUBOTA, H. , T. AIR.A and H. SAITO. On the sensitive color of chromatic polarization. J. opt. Soc. Am., 1951, 41 (8), 537-46.

LAND, E.H. Some aspects of the development of sheet polarizers. Symposium on Polarization, March i, 1951 Meeting of the Optical Society of America, Washington, D.C. Paper i. J. opt. Soc. Am., 1951, 41 (iZ), 957-63.

STEEL, W.H. TKe accuracy of polarization photometers. J. opt. Soc. Am., 1951, 41 (4), 223-8.

WEST, C.D., and R. CLARK JONES. On the properties of polarization elements as used in optical instruments. I. Fundamental consideration. Symposium on Polarization, March I, 1951 Meeting of the Optical Society of America, Washington, ID. C. Paper 4. J. opt. Soc. Am., 1951, 41 (iZ), 976-82.

Year 1952

ANON. No more glare from vehicle headiamps. Quick, Munich, 1952,

5 (49), 8.

ANON. Variable - color filters. J. opt. Soc. Am., 1952, 42 (9),

690-i.

52

CLANCY, E.P. Polarization effects in photomultiplier tubes. J. opt. Soc. A m . , 1952, 4__22 (5), 357.

HOCHSTRATE, W. The polarized dipped headlight. Lippstadt, 1952 (Hella) . (In German).

PETERS, C.W., and W.K. PIERSLEY. The use of wire gratings as polarizers. Thirty-Seventh Annual Meeting of the Optical Society of America, Boston, Massachusetts, 1952 (American Institute of Physics).

RAMACHANDRAN, G . N . , and S. RAMASESHAN. M a g n e t o - o p t i c ro t a t ion in b i r e f r i n g e n t m e d i a - app l i ca t i on of the P o i n c a r 4 s p h e r e . J. opt. Soc. Am., 1952, 42 (i), 49-56.

YAMAGUTI, T. s od ium n i t r a t e .

A s i m p l e m e t h o d ob ta in ing a l a r g e s i n g l e c r y s t a l of J. phys. Soc. Japan , 1952, [ , 113.

Y e a r 1953

ANON. L igh t con t ro l t h rough p o l a r i z a t i o n . J . opt. Soc. A m . , 1953, 43 (2), 149.

HAMMAD, A. Ca l cu l a t i on of the p o l a r i z a t i o n of a sun l i t sky c o m p o s e d of pure a i r m o l e c u l e s . J . opt. Soc. A m . , 1953, 4__33 (3), 184-7.

KERKER, M. , and M . J . HAMPTON. The u s e of u n f i l t e r e d l igh t in d e t e r m i n i n g p a r t i c l e r ad iu s by the p o l a r i z a t i o n r a t i o of the S c a t t e r e d l ight . J. opt. Soc. A m . , 1953, 43 (5), 370-2.

53

LAND, E.H. Three-dimensional presentation with polarized light. Thirty-eighth Annual Meeting of the Optical Society of America, Rochester, New York, October 15, 16, 17, 1953. Paper No. 49. New York, 1953 (American Institute of Physics).

Year 1954

CONN, G.K.T. , and G.K. EATON. On the use of a rotating polarizer to measure optical constants in the infrared. J. opt. Soc. Am., 1954,

44(6), 484-91.

CONN, G.K.T., and G.K. EATON. On polarization by transmission with particular reference to selenium films in the infrared. J. opt. Soc. Am., 1954, 44 (7), 553-7.

Year 1955

CHARNEY, E. Dichr0ic ratio measurements in the infrared region.

J. opt. Soc. Am., 1955, 45 (ii), 980-3.

54

KUBOTA, H. On hypersensitive polarization colors. J. opt. Soc. Am., 1955, 4Z (2), 144-5.

KUBOTA, H., and T. OSE. Further study of polarization and inter- ference colors. J. opt. Soc. Am., 1955, 42 (2), 89-97.

TSURUMI, I. Optical method for determining the small phase retardation with white light. J. opt. Soc. Am., 1955, 4-5 (iZ), 1021-3.

YAMAGUTI, T. On a sodium nitrate polarization plate of scattering type. J. opt. Soc. Am., 1955, 45 (i0), 891-2.

Year 1956

BAXTER, L. , A . S . MAKAS and W . A S H U R C L I F F . M e a s u r i n g • s p e c t r a l p r o p e r t i e s of h igh e x t i n c t i o n p o l a r i z e r s . J . opt. Soc. A m . , 1956, 46 (3), 229.

Year 1957

KUBOTA, H . , and K. S H I M I Z U . E x p e r i m e n t on the s e n s i t i v e c o l o r . j . opt. Soc. A m . , 1957, 47 ( i2) , 1121-3:

55

Year 1959

ANON. Response of a single retinula cell to polarized light. Nature, Lond., 1959, (4684), 455.

YAMAGUTI, T. Spectro-polarization characteristics of the sodium nitrate polarizer. J. phys. Soc. Japan. 1959, 14 (2), 199-201.

Year 1960

INGLESTAM, E. , and R. HEDMAN. Polarized headlights for cars. Statens trafiks&kerhetsrkd, Stockholm, 1960. (In Swedish).

Year 1961

SMITH, R.A. Improvements in or relating to devices for producing polarized illumination. British Patent Specification 880374. London 1961 (The Patent Office).

56

YAMAGUTI, T." Manufacturing method of po l a r i ze r s . Br i t i sh Patent Specification 862732. London, i 9 6 I (The Patent-Office).

Year 1962

CLARK JONES, R. Ultimate performance of polarizers for visible light. J. opt. Soc. Am., 1962, 52 (7), 747-52.

MAK_~S, A.S. Film polarizer for visible and ultraviolet radiation. J. opt. Soc. Am., 1962, 52 (I), 43-4. ~

Year 1963

KASEMAN, E. A new means of employing polarized automobile head- lights. Laboratory for Technical Physics Report. Oberandorf, Germany, 1963 (Laboratory for Technical Physics).

L • . • • .. :

57

MARK8, A.M. Imrpovements in and relating to light - polarizing vehicle windshield structures. British Patent Specification 926176. London, 1963 (The Patent Office).

YAMAGUTI, T. Improvements relating to the prevention of glare. British Patent Specification 918445. London, 1963 (The Patent Office).

Year 1964

DITCHBURN, R.W. Light. New York, 1964 (John Wiley & Sons, Inc).

HEIMBERGER, H. Improvements in or relating to anti-dazzle arrangements. British Patent Specification945881. London, 1964 (The Patent Office).

SHURCLIFF, W.A., and S.S. BALLARD. Polarized light. Princeton, New Jersey, 1964 (D. Van Nostrand Co. , Inc).

Year 1965

FRIED, D.L., and G.E. polarization fluctuation.

58

MEVERS. Atmospheric optical effects - J. opt. Soc. Am., 1965, 55 (6), 740-1.

MAKAS, A.S., and G.'R. BI'RD. Dichroic and reflective polarizer s in . lighting applications. Illum. Engng, N.Y., 1965, 60(4), 203-16.

SAXENA, A.N. Changes in the phase and amplitude of POlarized light reflected from a film-covered surface and their relations with the film thickness. J. opt. Soc. Am., 1965, 55 (9), 1061-7.

Year 1966

BERREMAN, D.W. Simple relation between reflectances of polarized components of a beam when the angle of incidence is 45 degrees. J. opt. Soc. Am., 1966, 56 (12), 1784.

HOLLADAY, T.M. , and J.D. GALLATIN. Phase control by polarization in coherent spatial filtering. J. opt. Soc. Am. , 56 (12), 869-72.

1966,

MARATHAY, A.S. Extension of the commutation relations in the theory of partial polarization. J. opt. Soc. Am. , 1966, 56 (5), 619-23.

TORRANCE, K.E., E.M. SPARROW and R.C. BIRKEBAK. Polarization, directional distribution, and off- specular peak phenomena in light reflected from •roughened surfaces. J. opt. Soc. Am., 1966, 5.._66 (7), 916-25.

59

Year 1967

BRYNGDAHL, O. Polarizing holography. J. opt. Soc. Am., 1967, 57 (4), 545-6.

HOLMES, D.A. Formula for calculating the refractive index from a thin transparent plate from polarization-state transmission measure- ments. 3. opt. Soc. Am., 1967, 5_~7 (4), 544-5.

McCOYD, G.C. surface model.

Polarization properties of a simple dielectric rough- J. opt. Soc. Am., 1967, 57 (ii), 1345-50.

VARGHESE, V.C. Reflection and refraction of light at internal and external faces of birefringent crystals. J. opt. Soc. Am., 1967, 57 (11), 1351-61.

Year 1968

BOROFKA, R.P., and P.F. O'BRIEN. Scene polarization measure- ments by photographic photometry, lllum. Engng, N.. Y. , 1968, 63 (8), 415-22.

DANDLIKER, R. Eigenstates of polarization in optical resonators with partial polarizers. J. opt. Soc. Am., 1968, 5__88 (8), 1062-9.

6O

KANO, M. skylight.

Effect of a concentrated turbid layer on the polarization of

J. opt. Soc. Am., 1968, 58(6), 789-97.

Year 1969

MOI%REN, L. The effect of polarization of light on the photometry of lighting fittings. Ltg Res Tech., 1969, 1 i), 53-4.

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(877) Dd635272 3M 6/70 H.P. Ltd., G1915 PRINTED IN ENGLAND

ABSTRACT

A bibliography with abstracts of research into the use of polarised headlights: L. COOPER: Ministry of Transport, RRL Report LR 343: Crowthorne, 1970 (Road Research Laboratory). Research undertaken at RRL since the first report was issued in 1949 is described by means of an annotated bibliography. Reports issued from other sources, together with a selected list of pertinent references, are given in a separate annotated bibliography.

ABSTRACT

A bibliography with abstracts of research into the use of polarised headlights: L. COOPER: Ministry of Transport, RRL Report LR 343: Crowthorne, 1970 (Road Research Laboratory). Research undertaken at RRL since the first report was issued in 1949 is described by means of an annotated bibliography. Reports issued from other sources, together with a selected list of pertinent references, are given in a separate annotated bibliography.