1. What are the objectives of traffic volume count? And discuss various traffic studies

Traffic volume count is the method in which the amount and direction of movement of traffic is obtained by different methods

a. Manual methodsb. Combination of manual and mechanical methodsc. Automatic devices

The various objective of conduction a volume count is as follows

1. Planning of highway activities2. Measurement of current demand3. Evaluation of existing traffic flow4. Planning of highway activities5. Measurement of current demand6. Evaluation of existing traffic flow7. Design of the geometric characteristics of a highway, for example, number of lanes,

intersection signalization, or channelization8. Capacity analysis 9. Development of programs related to traffic operations, for example, one-way street

systems or traffic routing10. Design of geometric characteristics, with particular reference to turning-radii

requirements, maximum grades, lane widths, and so forth11. Development of improvement and maintenance programs12. Development of freeway and major arterial street systems13. Evaluation of the economic feasibility of highway projects

Importance of Traffic Volume Study:Traffic survey is very important to be performed because it can

1. Increase the efficiency and life of roads2. Reduces traffic volume at a particular section3. Provide better means for development of infrastructures4. Provide better means to utilize other roads in case of special events in the city5. Provide estimate of no vehicles against no of persons

Types of volume studies Importance Presentation of data

Traffic volume studies 1. Planning2. Traffic

operation and control

3. Traffic pattern

4. Structural design of

Annual average daily traffic

Average daily traffic

Trend chart Variation

chart

pavements5. Regulatory

measures

Traffic flow maps

Highest hourly volume

Speed studies 1. Design various geometric elements

2. To conduct before and after studies

3. Traffic capacity

4. Accident studies

5. Planning traffic control and regulation

6. Speed trends

Average speed of vehicle

Cumulative speed

Modal average

Origin and destination studies 1. Plan the road network and other facilities for vehicular traffic

2. Plan and schedule of different modes of transportation for trip demand

Desire lines

Speed and delay studies 1. To assess before and after studies

2. Traffic capacity

Running speed

Overall speed

Fluctuations in speed

Delay between two stations

Traffic capacity study 1. Before and after studies

PCU/hr

2.Parking study 1. Parking

demand2. Parking

characteristics3. Parking space

inventory

Parking accumulation

Parking duration

Parking index

Parking volume

Accident study 1. To study the

cause of accident

2. To evaluate existing design

3. To carry out before and after studies

4.

Condition diagram

Collision diagram

2. Write a note on thirtieth highest hourly volume

The general unit of measuring traffic on highway is annual average daily traffic volume,

abbreviated as AADT. It is equal to the total annual volume of traffic divided by the number of

days in an year. A knowledge of traffic in terms of AADT is not of much use in geometric

design, since it does not represent the variation in traffic during months of an year, days of the

week, hours of a day. So commonly used unit for geometric design is the 30 th highest hourly

volume.

The 30th highest hourly volume is defined as the volume which is exceeded only 29 times in

a year and all other hourly volumes of the year will be less than this value. This value is

generally taken as the hourly volume for the design and will ensure that there will be

congestion only during 29 hours in a year.

3. Define PCU. List and explain the characteristics. Also mention recommended IRC values of PCU

The PCU may be considered as a measure of relative space required for a vehicle class compared

to that of a passenger car under a specified set of roadway, traffic and other conditions.

The PCU value of the vehicle class may be considered as the ratio of the capacity of a roadway

when there are passenger cars only to the capacity of the same roadway when there are vehicles

of that class only.

Factors affecting PCU values

The PCU values of different vehicle classes depend upon several factors. Some of these are listed

below.

1. Vehicles characteristics such as dimensions, power, speed, acceleration and bracking

characteristics

2. Transverse and longitudinal gaps or clearances between moving vehicles which depends

upon the speeds, driver characteristics and the vehicle clasees at the adjoining spaces.

3. Traffic stream characteristics such as composition of different vehicle classes, mean

speed and speed distribution of the mixed traffic stream, volume to capacity ratio

4. Roadway characteristics such as road geometrics including gradient, curve, etc. access

controls, rural or urban road, presence of intersections and the types of intersections

5. Regulation and control of traffic such as speed limits, one way traffic, presence of

different traffic control devices

6. Environmental and climatic conditions

Factors to be considered in the analysis of PCU

1. Average speed of the vehicle class under the prevailing roadway and traffic conditions

within the desired speed ranges

2. Average length and width of the vehicles

3. Average transverse and longitudinal gap between the vehicles of the same class

Type of vehicle PCU valuestwo wheelers 0.5Car 1Auto 1Bus , truck 3LCV 1.5Tractor with trailor 4.5Hand cart 3Horse cart 4Bullock cart 8

4. With a neat sketch explain the concept of origin and destination survey

Objectives of conducting Origin and destination studies

Plan the road network and other facilities for vehicular traffic Plan the schedule of different modes of transportation OD gives information about actual direction of travel, selection of routes and length of

trips To judge the adequacy of existing routes To identify the location suitable for expressways

Travel surveys are conducted to establish a complete understanding of the travel patterns within the study area. For single projects (such as a highway project), it may be sufficient to use traffic counts on existing roads or (for transit) counts of passengers riding the present system. However, to understand why people travel and where they wish to go, origin-destination (O-D) survey data can be useful. The O-D survey asks questions about each trip that is made on a specific day—such as where the trip begins and ends, the purpose of the trip, the time of day, and the vehicle involved (auto or transit)—and about the person making the trip—age, sex, income, vehicle owner, and so on.

The O-D survey may be completed as a home interview, or people may be asked questions while riding the bus or when stopped at a roadside interview station. Sometimes, the information is requested by telephone or by return postcard. O-D surveys are rarely completed in communities where these data have been previously collected.

O-D data are compared with other sources to ensure the accuracy and consis tency of the results. Among the comparisons used are crosschecks between the number of dwelling units or the trips per dwelling unit observed in the survey with published data. Screenline checks can be made to compare the number of reported trips that cross a defined boundary, such as a bridge or two parts of a city, with the number actually observed.

It is also possible to assign trips to the existing network to compare how well the data replicate actual travel. If the screenline crossings are significantly different from those produced by the data, it is possible to make adjustments in the O-D results so that conformance with the actual conditions is assured.

Different methods used to obtain O and D data are1. Roadside interview2. License plate3. Tag on car method4. Post card method5. Home interview method

Different ways of representing the results of origin and destination studies are listed below

1. Origin and destination tables showing number of trips between different zones2. Desire lines 3. Pie charts4. Contour lines

Desire line

Desire line is the graphical representation of the data collected from origin and destination survey, where in the location will be identified and lines are drawn connecting different locations the thickness of the line represents the number of trips occurring between the two locations. If the variation in the data is very small then we can also write numbers on top of the lines

connecting two points. Where the line represents the travel occurring between the locations and number represents the frequency.

5. With the help of sketches briefly explain on street parking

On-Street Parking FacilitiesThese are also known as curb facilities. Parking bays are provided alongside the curb on one or both sides of the street. These bays can be unrestricted parking facilities if the duration of parking is unlimited and parking is free, or they can be restricted parking facilities if parking is limited to specific times of the day for a maximum duration. Parking at restricted facilities may or may not be free. Restricted facilities also may be provided for specific purposes, such as to provide handicapped parking or as bus stops or loading bays.Common methods of on-street parking

1. Parallel parking2. 30º angle parking3. 45º angle parking4. 60º angle parking5. Right angle parking

Parallel parking consumes the maximum curb length which decreases as the angle of parking increases. The minimum curb length is consumed by the right angle parking, which accommodates nearly 2 times the number of vehicles as parallel parkingOn the other hand, parallel parking makes the least use of the width of the street and this is an important consideration in narrow streets. As the parking angle increases the width of street used also increasesFrom the point of view of manoeuvrability, angle parking seems to be better than parallel parking which usually involves a backing motion. Delay to traffic is minimum with angle parking

As regards safety, it has been noticed that angle parking is more hazardous than parallel parking

6. Define. a. Basic capacity b. Practice capacityc. Possible capacity

Basic capacity is the maximum number of vehicles(PCU) that can pass a given point on a lane or roadway during one hour under the most nearly ideal roadway and traffic conditions which can possibly be attained. Two roads have same physical features will have same basic capacities irrespective of the traffic conditions.

Possible Capacity is the maximum number of vehicles which can pass a given point on a lane or highway during one hour under the prevailing roadway and traffic conditions. This means that the possible capacity of a highway will always be lower than the basic capacity unless the prevailing conditions of the traffic, approach the ideal conditions. Therefore the possible capacity may vary from 0 to the maximum, i.e., Basic capacity.

Practical Capacity is the maximum number of vehicle that can pass a given point on a lane or roadway during one hour, without traffic density being so great as to cause unreasonable delay, hazard or restriction to the driver's freedom to man-oeuvre under the prevailing roadway and traffic conditions

7. Briefly explain procedure adopted in floating car method and analysis of data collected and representation of results

Moving-Vehicle Technique. In this method, the speed and flow can be obtained by travelling in a car against and with the flow, and noting down the journey time, the number of vehicles met with from the opposite direction, and number of vehicles overtaking the test vehicle and number of vehicles overtaken by the test vehicleA small, preferably even, number of test cars is required-usually two-each car carrying a driver and three observers. One observer in the car counts opposing traffic, using hand tallies. Another observer carries a recording board on which a watch is mounted. The recording board carries a journey log prepared in advance, on which the observer records the totals from the hand tallies and times at predermined point’s en-route, together with the times of stopping and starting at intersection. It is desirable to have two stop watches, one for recording the continuous time as the observer operates buttons. A third observer records the number of overtaking and overtaken vehicles, and if required, the number of parked vehicles. If only two observers are available, the driver is instructed to overtake as many vehicles as overtaken by him. The method is well suited to study the speeds along different roads in a area. Since conditions may vary from section to section on the route, the route is divided into convenient sections, say 0.75-1.5 km in length: it is desirable to have the ends of these sections at major intersections so that large discontinuities in speed and flow do not occur inside the section. It is desirable that twelve to sixteen runs in each direction along the route be made and the results averaged out so as to arrive at an accurate estimate of the speed and flow.Advantages of the method

1. The method gives an unbiased estimate of flow. Random errors can, however, occur due to observer’s errors and random fluctuations in flow, but these are not serious under normal conditions.

2. As compared to the stationary observer method, the moving observer method is equivalent to a stationary count over twice the single journey time. Hence it is economical in manpower.

3. It enables data on speed and flow to be collected at the same time. This is particularly advantageous when analysing the relations between the two.

4. It gives mean values of flow and speed over a section. Rather than at a point. Thus it gives directly the space mean speed, whereas spot speed studies gives the time measn speed.

5. It gives additional information on stops at intersections, delays, parked vehicles etc.

Analysis of the dataFlow q=xs+yn/ (ts+tn)q= volume along the direction of flowxs= volume of traffic in PCU moving in the opposite directionyn=overtaking vehicles minus over taken vehiclests= time required when moving in opposite to the flowtn= time required when moving along the flow

Time(Journey time)tn=tn- yn/qn

Representation of results1. Journey time2. Journey speed3. Running time4. Running speed5. Traffic flow in PCU/hr

8. Write a note of a. Condition diagramb. Collision diagramc. Off street parking

Collision DiagramsA collision diagram is a schematic representation of all accidents occurring at a given location over a specified period. Depending upon the accident frequency, the “specified period” usually ranges from one to three years. Each collision is represented by a set of arrows, one for each vehicle involved, which schematically represents the type of accident and directions of all vehicles. Arrows are generally labelled with codes indicating vehicle types, date and time of accident, and weather conditions. The arrows are placed on a schematic (not-to scale) drawing of the intersection with no interior details shown. One set of arrows represents one accident. It should be noted that arrows are not necessarily placed at the exact spot of the accident on the drawing. There could be several accidents that occurred at the same spot, but separate sets of arrows would be needed to depict them. Arrows illustrate the occurrence of the accident, and are placed as close to the actual spot of the accident as possible. Figure shows the standard symbols and codes used in the preparation of a typical collision diagram. Figure shows an illustrative collision diagram for an intersection. The collision diagram provides a powerful visual record of accident occurrence over a significant period of time. In Figure it is clear that the intersection has experienced primarily rear-end and right-angle collisions, with several injuries but no fatalities during the study period. Many of the accidents appear to be clustered at night. The diagram clearly points out these patterns, which now must be correlated to the physical and control characteristics of the site to determine contributing causes and appropriate corrective measures.

9.

Illustration of the collision diagram

Condition DiagramsA condition diagram describes all physical and environmental, conditions at the accident site. The diagram must show all geometric features of the site, the location and description of all control devices (signs, signals, markings, lighting, etc.), and all relevant features of the roadside environment, such as the location of driveways, roadside objects, land uses, etc. The diagram must encompass a large enough area around the location to include all potentially relevant features. This may range from several hundred feet on intersection approaches to .25-.50 mile on rural highway sections. Figure illustrates a condition diagram. It is for the same site and time period as the collision diagram of Figure. The diagram includes several hundred feet of each approach and shows all driveway locations and the commercial land uses they serve. Control details include signal locations and timing, location of all stop lines and crosswalks, and even the location of roadside trees, which could conceivably affect visibility of the signals.

Off-Street Parking FacilitiesThese facilities may be privately or publicly owned; they include surface lots and garages. Self-parking garages require that drivers park their own automobiles; attendant-parking garages maintain personnel to park the automobiles.The types of off-street facilities commonly considered are

1. surface car parks2. multi-storey car parks3. roof parks4. mechanical car parks5. underground car parks

There are some basic considerations which govern the location of these facilities. Since thse facilities are costly to provide and maintain, a comprehensive study should be done before hand to help determine the location, types and size of these facilities.

10. Write a note on a. Parking accumulationb. Parking indexc. Parking turnoverd. Parking volumee. Space hourf. Level of service

1. A space-hour is a unit of parking that defines the use of a single parking space for a period of 1 hour.2. Parking volume is the total number of vehicles that park in a study area during a specific length of time, usually a day.3. Parking accumulation is the number of parked vehicles in a study area at any specified time. These data can be plotted as a curve of parking accumulation against time, which shows the variation of the parking accumulation during the day.4. The parking load is the area under the accumulation curve between two specific times. It is usually given as the number of space-hours used during the specified period of time.5. Parking duration is the length of time a vehicle is parked at a parking bay. When the parking duration is given as an average, it gives an indication of how frequently a parking space becomes available.6. Parking turnover is the rate of use of a parking space. It is obtained by dividing the parking volume for a specified period by the number of parking spaces.7. Level of service: Level of service (LOS) is a qualitative measure used to relate the quality of traffic service. LOS is used to analyze highways by categorizing traffic flow and assigning quality levels of traffic based on performance measure like speed, density,etc

11. Define the term spot speed study. Explain the presentation of spot speed data

Spot speed is the instantaneous speed of a vehicle at a specified location. Spot speed can be used to design the geometry of road like horizontal and vertical curves, super elevation etc. The methods used for conducting spot speed studies can be grouped as under:

1. Those that require observation of time taken by a vehicle to cover a known distance.2. Radar speedometer which automatically records the instantaneous speed.3. Photographic method

First method can be further subdivided as1. those in which vehicles are timed over a long distance2. Those in which vehicles are timed over a short distance

The long base methods commonly used are.1. Direct timing procedure.2. Enoscope3. Pressure contact tubes

Recommended base lengthThe following base length for the long-base methods are adopted

Avg. Speed of Traffic Stream Base lengthLess than 40 27

40-65 54Greater than 65 81

Direct timing procedure for spot speed determinationThis is one of the simplest methods for spot speed determination. Two reference points are marked on the pavement at a suitable distance apart and an observer starts and stops and accurate stop watch as a vehicle crosses these two marks. From the known distance and the measured time intervals speeds are calculated. Skilled observers can read a stop-watch to an accuracy of 0.2 sec. if the observer stations himself inconspicuously, the speed readings are not influenced by driver reaction. The disadvantage with this method is that large errors are likely to be introduced because of the parallax effect.A simple variation of this method is to station two observers one at each reference point. The observer standing at the reference point which the vehicles pass first, signals that a vehicle to be timed is passing the the point and the second observer then starts a stopwatch. The second observer stops the stop watch when he observes the same vehicle passing the reference point. The disadvantage with this method is that it involves the reaction time of two individual observers.EnoscopeA simple device called Enoscope eliminates the parallax effect that creeps in when the direct readings are taken by one observer. This device, also known as the mirror-box is an L-shaped box, open at both ends, with a mirror set at a 45-degree angle to the arms of the instrument.The instrument bends the line of sight of the observer so that it is perpendicular to the path of the vehicle. The method can be used with one enoscope or with two enoscopes. If one enoscope is used, the instrument is placed directly opposite to the first reference point and the observer stations himself at the other reference point, The stop-watch is started as soon as the vehicle passes the first reference point and is topped as soon as it passes the observer. If two enoscopes are used, the observer stations himself mid-way between the two reference points and starts the stop- watch as soon as a vehicle crosses the second reference point

Pneumatic road tubes/ Pressure tubesAre laid across the lane in which data are to be collected. When a moving vehicle passes over the tube, an air impulse is transmitted through the tube to the counter. When used for speed measurements, two tubes are placed across the lane, usually about 6 ft apart. An impulse is recorded when the front wheels of a moving vehicle pass over the first tube; shortly afterward a second impulse is recorded when the front wheels pass over the second tube. The time elapsed between the two impulses and the distance between the tubes are used to compute the speed of the vehicle.

An inductive loop is a rectangular wire loop buried under the roadway surface. It usually serves as the detector of a resonant circuit. It operates on the principle that a disturbance in the electrical field is created when a motor vehicle passes across it. This causes a change in potential that is amplified, resulting in an impulse being sent to the counter.

Radar-Based Traffic SensorsRadar-based traffic sensors work on the principle that when a signal is transmitted onto a moving vehicle, the change in frequency between the transmitted signal and the reflected signal is proportional to the speed of the moving vehicle. The difference between the frequency of the transmitted signal and that of the reflected signal is measured by the equipment and then converted to speed in mi/h. In setting up the equipment, care must be taken to reduce the angle between the direction of the moving vehicle and the line joining the centre of the transmitter and the vehicle. The value of the speed recorded depends on that angle. If the angle is not zero, an error related to the cosine of that angle is introduced, resulting in a lower speed than that which would have been recorded if the angle had been zero. However, this error is not very large, because the cosines of small angles are not much less than one. So, The speed meter is so kept that the angle between the direction of travel of the vehicle and the axis of transmitted radio wave is as low as possible, say 20 degrees.The advantage of this method is that because pneumatic tubes are not used, if the equipment can be located at an inconspicuous position, the influence on driver behaviour is considerably reduced.

Electronic-Principle DetectorsIn this method, the presence of vehicles is detected through electronic means, and information on these vehicles is obtained, from which traffic characteristics, such as speed, volume, queues, and headways are computed. The great advantage of this method over the use of road detectors is that it is not necessary to physically install loops or any other type of detector on the road. A technology using electronics is video image processing, sometimes referred to as a machine-vision system. This system consists of an electronic camera overlooking a large section of the roadway and a microprocessor. The electronic camera receives the images from the road; the microprocessor determines the vehicle’s presence or passage. This information is then used to determine the traffic characteristics in real time. One such system is the autoscope.

Photographic method and video camera methodTime-lapse camera photography has been used successfully to determine the speed of vehicle accurately in crowded streets. According to this method, photographs are taken at fixed intervals of time (say one sec per frame) on a special camera. By projecting the film on a screen, the passage of any vehicle can be traced with reference to time. Images by video cameras can also be used.

12. Mention the various methods of carrying out speed and delay study. Explain any two of them

Several methods have been used to conduct travel time and delay studies. These methods can be grouped into two general categories: (1) those using a test vehicle and (2) those not requiring a

test vehicle. The particular technique used for any specific study depends on the reason for conducting the study and the available personnel and equipment.

Methods Requiring a Test VehicleThis category involves three possible techniques: floating-car, average-speed, and moving-vehicle techniques.Moving-Vehicle Technique. In this method, the speed and flow can be obtained by travelling in a car against and with the flow, and noting down the journey time, the number of vehicles met with from the opposite direction, and number of vehicles overtaking the test vehicle and number of vehicles overtaken by the test vehicleA small, preferably even, number of test cars is required-usually two-each car carrying a driver and three observers. One observer in the car counts opposing traffic, using hand tallies. Another observer carries a recording board on which a watch is mounted. The recording board carries a journey log prepared in advance, on which the observer records the totals from the hand tallies and times at predermined point’s en-route, together with the times of stopping and starting at intersection. It is desirable to have two stop watches, one for recording the continuous time as the observer operates buttons. A third observer records the number of overtaking and overtaken vehicles, and if required, the number of parked vehicles. If only two observers are available, the driver is instructed to overtake as many vehicles as overtaken by him. The method is well suited to study the speeds along different roads in a area. Since conditions may vary from section to section on the route, the route is divided into convenient sections, say 0.75-1.5 km in length: it is desirable to have the ends of these sections at major intersections so that large discontinuities in speed and flow do not occur inside the section. It is desirable that twelve to sixteen runs in each direction along the route be made and the results averaged out so as to arrive at an accurate estimate of the speed and flow.Advantages of the method

1. The method gives an unbiased estimate of flow. Random errors can, however, occur due to observer’s errors and random fluctuations in flow, but these are not serious under normal conditions.

2. As compared to the stationary observer method, the moving observer method is equivalent to a stationary count over twice the single journey time. Hence it is economical in manpower.

3. It enables data on speed and flow to be collected at the same time. This is particularly advantageous when analysing the relations between the two.

4. It gives mean values of flow and speed over a section. Rather than at a point. Thus it gives directly the space mean speed, whereas spot speed studies gives the time measn speed.

5. It gives additional information on stops at intersections, delays, parked vehicles etc.

Methods Not Requiring a Test VehicleThis category includes the license-plate method and the interview method.

License-Plate Observations. The license-plate method requires that observers be positioned at the beginning and end of the test section. Observers also can be positioned at other locations if elapsed times to those locations are required. Each observer records the last three or four digits of the license plate of each car that passes, together with the time at which the car passes. The reduction of the data is accomplished in the office by matching the times of arrival at the beginning and end of the test section for each license plate recorded. The difference between these times is the travelling time of each vehicle. The average of these is the average travelling time on the test section. It has been suggested that a sample size of 50 matched license plates will give reasonably accurate results. The section can be divided into stretches of 0.5 to 1.00 km length. The accuracy of the data collected from this method is about +98-99%. Two observers can record the data at the rate of about 300 vehicles per hour.The advantages of this method is that no sophisticated instruments are needed except stop watches. The analysis is how-ever, laborious and time consuming, but can be rendered easily with the help of computers. The method can only be used on highway sections having minor or no intersections, since the vehicles may enter, leave or stop within the section having intersections. Hence this method is suitable for rural roads.

Elevated observer methodIn this method, the observer stationed on top of the elevated building select vehicles at random and follow their course along the road, noting the time of entering the section, duration and nature of delays suffered and the time of leaving. The test section has to be short, such as a street in central area of a city.

Interviews. The interviewing method is carried out by obtaining information from people on the study site regarding their travel times, their experience of delays, and so forth. who drive This method facilitates the collection of a large amount of data in a relatively short time. However, it requires the cooperation of the people contacted, since the result depends entirely on the information given by them.

13. Mention the objectives of accident studies. Also mention the various causes of accidents

Objectives1. To identify causes and suggest remedial measures at black spots ( where accidents are

frequented)2. Evaluate the existing system and proposed redesign or new design to improve road safety3. Carry out Before and after studies for analysis and assessing the change in system4. Workout accident cost,(direct and indirect) and financial losses5. Economic justification for the improved proposals.6. To workout benefit cost ratio

CausesRoad, vehicle, driver and environment are the main causes in which pedestrians, road users( violation of rules, carelessness of movement), and passengers(alighting and boarding moving vehicles), animals, and other( sign, signals, badly located advance boards etc)

DriverThe human causes attribute to about 60-85% accidents. The following are some of the reasons.

1. Excessive or very low speeds2. Following too closely behind another vehicle3. Not keeping to the left while driving4. Failure to keep lanes and haphazard crossing of lanes5. Failure to give signals for stop, turn and overtake vehicles.6. Overtaking dangerously7. Ignoring traffic lights and signals8. Moving against one way9. Driving under influence10. Impatience to traffic11. Distraction, conservation while driving, loud music while driving etc12. Use of cell phone while driving13. Driving a two wheeler without a helmet14. Poor vision and lack of hearing

Vehicles1. Brake failure, headlights, taillight, parking light and indicators not in order2. Bald and poorly inflated tires, inadequate fuel, brake oil, fuel oil3. Ineffective steering, non adjusted rear view mirror4. Carrying more passengers than recommended5. Exceeding in length, height width than prescribed6. Exceeding the legal axle weight7. 2 wheeler without sari gaurds8. Not using seat belts9. Bad working condition of wiper10. Dark sunfilm of glasses11. Public vehicles without white reflector at front.12. Gas cylinders not properly secured

Road1. Poorly designed and maintained roads2. Poor visibility3. Poorly illuminated roads4. Improper and insufficient road geometrics5. Inadequate road signs and improper location6. Faulty design, improper location and not properly painted and illuminated speed

breakers.7. Improper medians and kerbs8. Pot holes and man holes9. Oil spilled road surface10. Road side low level tree branches11. Bottle neck along the roads12. Gradients of roads13. Inadequate road width

EnvironmentExcessive wind, time of the day, fog, landslides and rain may be some of the causes

14. Definea. Running speedb. Space-mean speedc. Time mean speedd. Delay

Running speed is the average speed maintained by a vehicle over given course while the vehicle is in motion. It is significant to note the clause, while the vehicle is in motion’. Because the running speed is obtained by dividing the length of course by the time the vehicle is in motion, i.e. by the running time, which excludes that part of the journey time when the vehicle suffers delay. Thus,

Running speed=length of course Running time

=length of course Journey time- delay

Journey speed, also known as overall travel speed, is the effective speed of a vehicle between two points, and is the distance between two points divided by the total time taken by the vehicle to complete the journey, including all delays incurred en-route. Thus:Journey speed= distance .

Total journey time (including delays)

Time-mean speed is the average speed measurement at one point in space over a period of the time. It is the average of a number of spot speed measurements

Space-mean speed is the average of the speed measurements at an instance of time over a space.

Delay: it is the amount of time during which the vehicle is forced to stop because of traffic congestion, accident etc

15. Enumerate the different methods of traffic volume studies

Methods of volume countThe methods available for conduction traffic counts are listed below

1. Manual methods2. Combination of manual and mechanical methods3. Automatic devices

Manual methods use field personnel to count and classify traffic flowing past a fixed point. Automatic devices enable a count of traffic to be taken at any given location and a record to be kept of the count.Number of observersThe number of observers needed to count the vehicles depends upon the number of lanes in the highway on which the count is to be taken and the type of information desired. The indications are given in the table below

Road Features and counting requirements No of vehicles per hour that can be counted by one trained observer

2-Lane tow-way road, with separate observers for each direction: vehicles to be counted and classified

500 vehicles per hour in one direction

2 lane two-way road, with one observer for both directions: vehicles to be counted and classified for each direction seperatly

200 vehicles per hour in both directions

2 lane two-way road, with one observer for both directions: vehicles to be simply counted with no requirement for classification and posting into separate direction

800 vehicles per hour both direction

Equipments neededThe following equipments are needed

1. A watch2. Pencils, eraser and pencil sharpener3. Supply of blank field data sheets4. Clip board

MethodologyManual counting involves one or more persons recording observed vehicles using a counter. With this type of counter, both the turning movements at the intersection and the types of vehicles can be recorded. Note that in general, the inclusion of pickups and light trucks with four tires in the category of passenger cars does not create any significant deficiencies in the data collected, since the performance characteristics of these vehicles are similar to those of passenger cars. In some instances, however, a more detailed breakdown of commercial vehicles may be required which would necessitate the collection of data according to number of axles and/or weight. However, the degree of truck classification usually depends on the anticipated use of the data collected. Traffic flowing past a survey point is counted by an observer, who would record the flow using either a tally counter or by taking a manual count of vehicles and recording it on paper, typically using a five bar gate counting technique, or by using a hand-held computer. Counts are classified, to identify the volume and mix of types of vehicles using the road at the survey point. However, the level of classification used will very much depend upon the needs of the survey. For example, it may be adequate to use a simpler form of classification, such as cars and taxis, buses and commercial vehicles. The engineer should choose an appropriate level of classification for each study. If a data collection survey is only planned to cover a short period of time, then the expense of installing an automatic counter may not be justified when compared with the cost of using a surveyor. The surveyor also has the ability to discriminate between classes of vehicles. Manual counts generally offer better value for money when data is to required for a single day or for less than the full 24-hour day but collected over 2 or 3 days. Manual classified counts(MCCs) become more difficult where flows are very high, and where any break in concentration can introduce high error rates in the count. If the engineer wishes to gain a quick insight to traffic conditions over a wider area, short period, sample traffic counts can be taken over a wide area and factored up, to represent the hourly flow. Thus, for example, if one wished to have an understanding of traffic levels at a complex junction, traffic could be counted

at each arm for 5–10 minutes and then factored up to hourly counts, to give an understanding of conditions. This is a good method of gaining a quick insight into traffic levels but should not be used as a substitute for a properly organised traffic survey.

The Advantages of manual methods and situations where these are to be preferred are:1. Details such as vehicle classification and number of occupants can be easily obtained.

With automatic devices these data are unfortunately lacking, and hence automatic counting should be supported by manual counts.

2. The data can be collected giving the breckdown of traffic in each direction of travel3. Specific vehicular movements such as left-turns, right-turns, straight- aheads etc. at a

junction can be noted and recorded.4. Manual methods enable any unusual conditions obtaining at the time of count to be

recorded. This will help in understanding and analysing the traffic characteristics. Such, unusual conditions can be adverse weather conditions, traffic breckdowns, temporary closure of any lane of the highway for maintenance operations etc.

5. In developing countries, sophisticated automatic devices are not indigenously produced. On the other hand, manpower for counting is available comparatively cheaply

6. Pilferage and vandalism often prevent the use of costly equipments in remote rural areas, and in such cases manual methods are the only solution

7. Even if automatic devices are used, it is often necessary to check the accuracy of these devices periodically and manual methods serve this purpose

8. Data accumulated by manual methods are easy to analyse9. Manual methods are suitable for short-term and non continuous counts.

The main disadvantages of the manual count method are that (1) it is labour intensive and therefore can be expensive, (2) it is subject to the limitations of human factors, and (3) it cannot be used for long periods of counting.

Combination of manual and mechanical methodAn example of a combination of manual and mechanical methods is the multiple pen recorders. A chart moves continuously at the speed of a clock. Different pens record the occurrence of different events on the chart. The actuation of the event recorder pen is by pressing the electric switch associated with each pen recorder. For instance, a particular switch may be pressed whenever a particular class of vehicles arrives and this operates the per on the channel which can be identified with the arrival of a particular class of vehicle. The advantages of this method are

1. A permanent record is kept of the arrival of each class of vehicle. The classification and vehicle count are performed simultaneously

2. Additional information such as time-headway between successive vehicles and the arrivals per unit time become available

Automatic DevicesSensorsSensors operated on several different principles are available

1. Pneumatic tube: a flexible tube with one end sealed is clamped to the road surface at right angles to the pavement. The other end of the tube is connected to a diaphragm actuated switch. When an axle of a vehicle crosses the tube, a volume of air gets displaced thus creating a pressure which instantaneously closes the electrical contact

through the switch. Two such contacts results in one count being registered, thus representing the two axles in a vehicle. Inaccuracies are caused when vehicles with more than two axles are present in the traffic stream in appreciable number. Because of their simplicity and their cheapness, pneumatic tube sensors are very popular. Some difficulty may be caused in fixing them to gravel surfaces and they have additional drawback that they are easily pilfered by vandals. They are likely to be damaged by crawler tractors, tyre chains, snow ploughs and similar equipments. They cannot detect vehicles by lanes

2. Electric contact: a pair of steel strips are contained in a rubber pad which is buried beneath the surface. On being pressed by the weight of a moving axle the steel strips come into contact with each other and cause the electric current to flow. Electric contact detectors, while retaining the advantages and disadvantages of pneumatic tube detectors, have the ability to detect vehicles in individual lanes

3. Co-axial cable: a co-axial cable is clamped across the road surface, with the capability of generating signals with the passage of axles. These signals actuate a transistorised counter. The advantages associated with this type of detectors are their better reliability and performance on inferior type of surfaces and their lesser susceptibility to damage

4. Photo-electric: on one end of the road is a source of light which emits a beam across the road. At the other end is a photo-cell which can distinguish between the light beam and absence of light beam. The passage of a vehicle in the path of the light beam obstructs the beam and causes detection by photo-cell. The difficulty with this otherwise simple technique is that obstruction can be caused by pedestrians and that more than one vehicle in the different traffic lanes, but position in the line of the beam simultaneously, will register only one vehicle

5. Radar: Doppler Effect is a well-known phenomenon in physics which enables detection of vehicles moving at a speed. When a moving object approaches or recedes from the moving object will be different from the frequency of the signal emitted by the source. This difference in the two frequencies causes detection of a moving object. The initial cost of this device is no doubt high, but its accuracy and reliability, a part from its non-susceptibility to damage by traffic, have much to appeal.

6. Infra-red and ultrasonic. Infrared sensors can detect the heat radiated from a vehicle or can react to the reflection from the vehicle of infra-red radiation emitted by the sensonrs

16. Explain different measures through which accidents can be minimized

RemediesTo improve the safety on the roads we have to follow 3 E’s engineering, enforcement and education.

EngineeringFor the roads to be safer we have to first design geometrics of the road along with all other features properly like, road width, lane width, easy gradients, horizontal and vertical curves, intersection design (channelization), pavement surface characteristics, skid resistance, service road condition arterial road, one way system, adequate footpath, flyovers, subways, raised kerbs,.medians with grill, street lighting, speed breakers, marking, cutting tree branches.

EnforcementDone by enforcement officers- traffic and transport officials to book violators, speed controls, radar gun to measure speeding and challenging to book drink and driving cases, traffic rules, regulations and control, installation of signals, signages and enforcing them, lane discipline, markings, channalizination, creation of islands, strict issue of Driving licenses, medical checkups and fitness certificate.

Education:This is important to bring traffic awareness and safety, pedestrian, passengers and road users to follow tips for diffensive driving, education to children through posters, banners etc, zebra crossing, periodic training to all the road users, by lectures, exhibition, workshops etc.

17. List and explain different types of volumes counts

Different types of traffic counts are carried out, depending on the anticipated use of the data to be collected. These different types will now be briefly discussed.

Cordon and screen-line surveyThese provide useful information about trips from and to external zones. For large study area, internal cordon-line can be needed and surveying can be conducted.The objective of the survey is primarily to collect the origin and destination zones and for this many suitable methods can be adopted. It could be either recording the license plate number at all the external cordon points or by post-card method. Screen lines divide the study area into large natural zones, like either sides of a river, with few crossing points between them.The procedure for both cordon-line and screen-line survey are similar to road-side interview. However, these counts are primarily used for calibration and validation of the models.

Intersection CountsIntersection counts are taken to determine vehicle classifications, through movements, and turning movements at intersections. These data are used mainly in determining phase lengths and cycle times for signalized intersections, in the design of channelization at intersections, and in the general design of improvements to intersections.

Pedestrian Volume CountsVolume counts of pedestrians are made at locations such as subway stations, midblocks, and crosswalks. The counts are usually taken at these locations when the evaluation of existing or proposed pedestrian facilities is to be undertaken. Such facilities may include pedestrian overpasses or underpasses. Pedestrian counts can be made using the TDC-12 electronic manual counter described earlier and shown in Figure 4.7. The locations at which pedestrian counts are taken also include intersections, along sidewalks, and mid-block crossings. These counts can be used for crash analysis, capacity analysis, and determining minimum signal timings at signalized intersections.

Periodic Volume CountsIn order to obtain certain traffic volume data, such as AADT, it is necessary to obtain data continuously. However, it is not feasible to collect continuous data on all roads because of the cost involved. To make reasonable estimates of annual traffic volume characteristics on an area-wide basis, different types of periodic counts, with count durations ranging from 15 minutes to continuous, are conducted; the data from these different periodic counts are used to determine values that are then employed in the estimation of annual traffic characteristics. The periodic counts usually conducted are continuous, control, or coverage counts.

Continuous Counts. These counts are taken continuously using mechanical or electronic counters. Stations at which continuous counts are taken are known as permanent count stations. In selecting permanent count

stations, the highways within the study area must first be properly classified. Each class should consist of highway links with similar traffic patterns and characteristics. A highway link is defined for traffic count purposes as a homogeneous section that has the same traffic characteristics, such as AADT and daily, weekly, and seasonal variations in traffic volumes at each point. Broad classification systems for major roads may include freeways, expressways, and major arterials. For minor roads, classifications may include residential, commercial, and industrial streets.

Control Counts. These counts are taken at stations known as control-count stations, which are strategically located so that representative samples of traffic volume can be taken on each type of highway or street in an area-wide traffic counting program. The data obtained from control counts are used to determine seasonal and monthly variations of traffic characteristics so that expansion factors can be determined.These expansion factors are used to determine year-round average values from short counts. Control counts can be divided into major and minor control counts. Major control counts are taken monthly, with 24-hour directional counts taken on at least three days during the week (Tuesday, Wednesday, and Thursday) and also on Saturday and Sunday to obtain information on weekend volumes. It is usual to locate at least one major control-count station on every major street. The data collected give information regarding hourly, monthly, and seasonal variations of traffic characteristics. Minor control counts are five-day weekday counts taken every other month on minor roads.

Coverage Counts. These counts are used to estimate ADT, using expansion factors developed from control counts. The study area is usually divided into zones that have similar traffic characteristics. At least one coverage count station is located in each zone. A 24-hour non-directional weekday count is taken at least once every four years at each coverage station. The data indicate changes in area-wide traffic characteristics.

18. Explain the representation of volume count

Traffic Volume Data PresentationThe data collected from traffic volume counts may be presented in one of several ways, depending on the type of count conducted and the primary use of the data. Descriptions of some of the conventional data presentation techniques follow.

Traffic Flow MapsThese maps show traffic volumes on individual routes. The volume of traffic on each route is represented by the width of a band, which is drawn in proportion to the traffic volume it represents, providing a graphic representation of the different volumes that facilitates easy visualization of the relative volumes of traffic on different routes. When flows are significantly different in opposite directions on a particular street or highway, it is advisable to provide a separate band for each direction. In order to increase the usefulness of such maps, the numerical

value represented by each band is listed near the band. Figure 4.13 shows a typical traffic flow map.Intersection Summary SheetsThese sheets are graphic representations of the volume and directions of all traffic movements through the intersection. These volumes can be either ADTs or PHVs, depending on the use of the data. Figure 4.14 shows a typical intersection summary sheet, displaying peak-hour traffic through the intersection.

Time-Based Distribution ChartsThese charts show the hourly, daily, monthly, or annual variations in traffic volume in an area or on a particular highway. Each volume is usually given as a percentage of the average volume. Figure 4.15 shows typical charts for monthly, daily, and hourly variations.

Figure 4.13 Example of a Traffic Figure 4.14 Intersection Summary Sheet

Flow Map

19. Define traffic capacity? List the factors affecting capacity

It is the ability to accommodate traffic volume. It is the maximum hourly rate at which vehicles can reasonably be expected to cross a point on a roadway during a given time period under prevailing traffic conditions

Factors affecting highway capacity1. Lane width2. Width of the shoulders3. Lateral clearance4. Commercial vehicles5. Road alignment and geometry6. Existence of intersection7. One way or two way traffic

8. Driver and vehicle characteristics9. Speed10. Weather condition11. Parking condition12. Presence of pedestrians