rankers - trimis.ec.europa.eu · d4.2 road safety index tren-04-fp6tr-s07.36996/001678 d4.2 ii...

ranking for european road safetyrankers

Sustainable Surface Transport RANKING FOR EUROPEAN ROAD SAFEY SIXTH FRAMEWORK PROGRAMME SPECIFIC TARGETED RESEARCH OR INNOVATION PROJECT TREN-04-FP6TR-S07.36996/001678

Deliverable No D4.2 Deliverable name Road Safety Index

Workpackage 4 Version number Final Lead participant CIDAUT

Dissemination level PU Due date of deliverable 31.01.2008

File name D4.2

Authors

José Miguel Perandones, Guillermo Ramos, CIDAUT

WP Leader

Robert Thomson, CHALMERS

STREP Coordinator

Guillermo Ramos Fundación CIDAUT Parque Tecnológico de Boecillo, P. 209 47151 Boecillo (Valladolid) / SPAIN Phone + 34 983 54 80 35 Mobile + 34 678 46 79 81 Fax + 34 983 54 80 62 E-mail [email protected]

rankers D4.2 Road Safety Index TREN-04-FP6TR-S07.36996/001678

D4.2 i

Revision chart and history log

Version Date Description

1 01/08/07 Structure of the document

2 09/01/2008 Draft version

Final 31/07/2008 Final version released to consortium for final review


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Table of contents

REVISION CHART AND HISTORY LOG.................................................................................................... I TABLE OF CONTENTS.........................................................................................................................II LIST OF FIGURES & TABLES.............................................................................................................. III 1. INTRODUCTION ....................................................................................................................... 1 2. THE ROAD SAFETY INDEX: OBJECTIVE AND METHODOLOGY...................................................... 3 3. RSI ROAD INFRASTRUCTURE TOPICS...................................................................................... 10

3.1. Road Alignment ........................................................................................................ 10 3.2. Road junctions – private accesses ......................................................................... 13 3.3. OVERTAKING............................................................................................................ 15 3.4. ROADSIDE ................................................................................................................ 17 3.5. PAVEMENT & SUPERELEVATION .......................................................................... 20 3.6. CONSISTENCY.......................................................................................................... 22

4. RSI PROCEDURE OF APPLICATION ......................................................................................... 24 4.1. Definition of the road sections ................................................................................ 24 4.2. Collection of data ..................................................................................................... 24 4.3. Application of the RSI to each road section........................................................... 25 4.4. Accident correction factors for average marks ..................................................... 26

5. APPLICATION OF THE RSI TO A REAL ROAD ............................................................................ 28 5.1. Road Alignment ........................................................................................................ 28 5.2. Road Accesses......................................................................................................... 30 5.3. Overtaking................................................................................................................. 32 5.4. Roadside ................................................................................................................... 34 5.5. Pavement & Superelevation .................................................................................... 36 5.6. Consistency .............................................................................................................. 36 5.7. Identification of road infrastructure safety priorities in the road ......................... 37

6. MAIN DIFFICULTIES AND RESEARCH NEEDS ............................................................................. 39 7. CONCLUSIONS...................................................................................................................... 40 I. RSI APPLICATION RESULTS ................................................................................................... 42


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List of Figures & Tables

Table 1 Ce values related to hazard distance to carriageway ...................................................... 17 Table 2 Ca values related to hazard crashworthiness .................................................................. 17 Table 3 RSI roadisde mark definition ........................................................................................... 18 Table 4 RSI application results to a road section ......................................................................... 25 Table 5 CF calculation for each road section............................................................................... 27 Table 6 RSI marks of the road by road section and road infrastructure topic............................... 38 Table 7 RSI results for road section 1.......................................................................................... 42 Table 8 RSI results for road section 2.......................................................................................... 43 Table 9 RSI results for road section 3.......................................................................................... 44 Table 10 RSI results for road section 4........................................................................................ 45 Table 11 RSI results for road section 5........................................................................................ 46 Table 12 RSI results for road section 6........................................................................................ 47 Table 13 RSI results for road section 7........................................................................................ 48 Table 14 RSI results for road section 8........................................................................................ 49 Table 15 RSI results for road section 9........................................................................................ 50 Table 16 RSI results for road section 10...................................................................................... 51 Table 17 RSI results for road section 11...................................................................................... 52 Table 18 RSI results for road section 12...................................................................................... 53 Table 19 RSI results for road section 13...................................................................................... 54 Table 20 RSI results for road section 14...................................................................................... 55 Table 21 RSI results for road section 15...................................................................................... 56 Table 22 RSI results for road section 16...................................................................................... 57 Table 23 RSI results for road section 17...................................................................................... 58 Figure 1 RSI road infrastructure topics .......................................................................................... 3 Figure 2 RSI colour evaluation scale ............................................................................................. 4 Figure 3 Road section evaluation results example......................................................................... 5 Figure 4 Example of the evaluation results after applying the RSI to a set of roads ...................... 6 Figure 5 Castilla y León Regional road network inventory software............................................... 8 Figure 6 Road Alignment RSI marks by road section .................................................................. 29 Figure 7 Poor pavement status in road section 14....................................................................... 29 Figure 8 Road Accesses RSI marks by road section ................................................................... 30 Figure 9 Road Accesses deficiencies in road sections 4 & 6 ....................................................... 31 Figure 10 Overtaking marks by road section................................................................................ 32 Figure 11 Overtaking allowed in section 8 when there is not enough visibility ............................. 33


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Figure 12 Roadside marks by road section.................................................................................. 34 Figure 13 Tree too to close to the carriageway (road section 3) & concrete culvert (road section 4)..................................................................................................................................................... 35 Figure 14 Pavement & Superelevation marks by road section..................................................... 36 Figure 15 Consistency marks by road section ............................................................................. 37 Figure 1 RSI road infrastructure topics ........................................................................................ 38


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1. Introduction

One of the two main objectives of the RANKERS Project is to develop a Road Safety Index able to identify those road sections with infrastructure deficiencies. This index would allow solving road safety problems before they become traffic accidents and is aimed at analysing each feature of the road infrastructure in order to detect what aspects of the road features might be enhanced. With almost one third of road traffic accident fatalities in single vehicle accidents, where road infrastructure plays a major role on the outcome itself and the outcome of the accident, road infrastructure is a major actor on road safety. It should not be concluded that road infrastructure only influences the single vehicle accidents mentioned previously. In fact, the casualties associated with single vehicle accidents is just a minimum threshold of the fatalities that can be influenced by road infrastructure improvements. During the last decades, the automotive industry has invested significant research resources for systems protecting vehicle occupants and other road users like pedestrians. These activities have produced an enhancement to the level of safety most vehicles offer. Different types of airbags, active safety systems like advanced brake systems, the ESC (Electronic Stability Control) are just some examples. However, theses efforts are usually conducted independent of research developments for the improvement of road infrastructure safety. Initiatives of different scopes have been undertaken in order to increase the level of road safety through the enhancement of road infrastructure. On the one hand, the European Commission submitted a proposal to the European Parliament on Road Infrastructure Safety Management. This directive has recently been approved and is aimed at promoting safety at all the stages of a road section lifetime: planning, design, construction and operation. By introducing different tools such as Road Impact Assessment, Road Safety Audits and Inspections and Black Spots Management, this directive promotes an integrated concept of safety also within the road infrastructure field. Indeed, the sooner safety is considered in road networks lifetime the cheaper it becomes. On the other hand, and trying to emulate the success of the EuroNCAP initiative, EuroRAP was launched at the beginning of this decade, a program aimed at evaluating safety on road sections by applying a star rating depending on the infrastructure quality (http://www.eurorap.org/). The two preceding are just examples of how to incorporate road infrastructure components into a plan to improve road safety. RANKERS has intended to go a step beyond the analysis and inspection of road infrastructures by also providing scientific based tools to conduct detailed analyses of the influence of infrastructure devices in road safety.


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This deliverable presents the Road Safety Index, the methodology to be applied and the results of an application performed with a real road section. The report is structured as follows:

• Chapter 2 presents the objectives of the RSI and an overview of the methodology followed and the structure of the index. It also provides some examples of the potential results and applications of the index.

• Chapter 3 is aimed at presenting how the RSI evaluates each road infrastructure topic (Road alignment, roadside, junctions, pavement, overtaking and road layout consistency).

• Chapter 4 gives an overview on how to calculate the marks and average marks for each road infrastructure topic and also for each road section.

• In Chapter 5 it is presented the main results of the application of the RSI to a real road section within the regional road network of Castilla y León.

• The main difficulties found when developing the RSI and future research needs for the improvement of the index are described in Chapter 6.

• Finally, Chapter 7 gives a summary of the main conclusions of the activities performed to develop the RSI.


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2. The Road Safety Index: Objective and Methodology

The main objective of the Road Safety Index (RSI) is to develop a methodology to identify road sections with road infrastructure deficiencies related to road safety through:

• Road inspections. • Road maintenance data. • Road video recording. • Road inventory software analysis. • The use of complementary data: traffic flow, type of road network, accident data, etc.

Therefore, the approach of the RSI is proactive and is aimed at preventing future road accidents where road infrastructure might be improved. Nevertheless, there is a wide range of road infrastructure topics that needs to be considered. Therefore, the RSI analyses road infrastructure divided in six different topics, so it can provide not only a general evaluation of the road infrastructure in a road section but also the specific road infrastructure topics that might need of safety enhancements. Moreover, this may permit also to better identify the best countermeasures to be implemented when a road is assessed with the RSI (for example through the application of the Ranking of Recommendations that RANKERS has also developed). The above mentioned infrastructure topics are shown in Figure 1.

ROAD ALIGNMENT: lanes & shoulder width, curvature radius, visibility, etc.

ROADSIDE: geometry, presence of obstacles and distance to the carriageway, safety equipment,, etc.

JUNCTIONS: nº of junctions present, nº of private accesses and their coordination, level of signing at intersections, etc.

PAVEMENT: assessment of the pavement status, superelevation coordination and transition in curves, etc.

OVERTAKING: coherence between road marking – vertical signs, available visibility for overtaking manoeuvres.

ROAD LAYOUT CONSISTENCY: relationship between curvature of consecutive curves, drivers’ perception, etc.

Figure 1 RSI road infrastructure topics


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Once the different topics to be assessed are defined there are two important issues to be also specified:

• RSI road section length The length of application of the RSI must be long enough to be cost – effective but it must also be short enough so any compensation effect within too long sections can be avoided. Therefore, a length between 1.5 – 2 km. has been selected for the RSI. This means that the RSI will provide an evaluation for road sections of that length, divided in the six different topics presented above.

• How to define the assessment of each topic, bearing in mind that they are different, so they can be compared across the road network? This index is aimed at assessing the influence of different topics in road safety. Therefore, we need to define a common evaluation scale so we can both compare the same topic in different road sections and different topics within the same road section. With that approach, one of the RANKERS objectives will be accomplished, which is to provide a tool to road administrations to detect road deficiencies but allowing at the same time to prioritize the most urgent problems to be tackled. It was deemed that the best way to define this evaluation scale was to base it on the urgency of actuation that each deficiency showed when applying the RSI. Four marking options were defined as follows (1 being the worst and 4 the best): 1. It is urgent to take remedial measures to solve this infrastructure safety topic. 2. There are deficiencies to be solved in a medium term period. 3. No need of action if maintenance is kept properly. 4. No action is necessary. For each road infrastructure topic, there are different questions that tackle all that has to be considered within it (i.e.: in road alignment there will be questions for lane width, shoulder width, etc.). Therefore there will be a mark for each issue. In order to provide an evaluation of the whole topic, an average of the different issues is calculated. Logically, this average will always be comprised between 1 and 4. In order to make it easier to map the results, a colour scale has been defined in order to present this average for each topic and each road section as is shown in Figure 2.

4 ≥ Mark >3

3 ≥ Mark >2

2 ≥ Mark >1

Figure 2 RSI colour evaluation scale


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Therefore, after applying the RSI to a road section, an evaluation for each of the six infrastructure topics is obtained and therefore can be translated to the above colour scale. An overall average of the road section can be also calculated by showing the average of the six topics evaluation. In the Figure 3 an example of the evaluation results for a road section is shown.

Figure 3 Road section evaluation results example

At this stage we can already present the potential application of the RSI. Once it is applied to a set of road of a road network, through the map presented in Figure 4, a road administrator could detect the road sections with lowest average score and also those with lowest score for each road infrastructure topic. This will help to define where is most necessary to implement countermeasures, for instance, on the roadside or where investments should be made on improving the road layout or junctions design. It can be seen that each road is divided in as many road sections as needed in order to apply the RSI.


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Figure 4 Example of the evaluation results after applying the RSI to a set of roads

In order to properly assess all the different infrastructure issues a wide set of data is necessary. Due to the fact that these data are of different nature, the following tools are recommended to be used when applying the RSI:

A) Road safety inspections Visiting road sections is necessary in order to get a first overview of the road sections to be assessed. Road safety experts are able to detect in those inspections the main deficiencies of the road, both by driving and walking on particular road sections. They are also able to observe users’ behaviour in order to detect what aspects of the infrastructure may induce wrong behaviours in users. Experts are able to review the following aspects among others:

- Unprotected roadside obstacles and their geometry. - Road layout conflict points due to the curvature, unexpected design features, signing

deficiencies, etc. - Visibility problems due to the environment or the roadside. - Infrastructure problems related to adverse weather conditions like water

accumulation due to a wrong superelevation design on the pavement. - Road users’ behaviour at conflict points. - Road signing status and performance (conducted under a range of lighting and

weather conditions). - Specific requirements for vulnerable road users (pedestrians, cyclists and

motorcycles).


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Visiting road sections is recommended not only for the application of the RSI but also before implementing any road infrastructure countermeasure. Although one might know the expected behaviour of the countermeasure in similar locations, it is necessary to check in situ the specific situation of the road stretch. For instance this may avoid solving apparently the problem in a particular section when indeed it has been moved to another road section close to it. B) Road video recording

Unfortunately road safety inspections are limited in terms of time and the road section might not always as close to the experts headquarters as desired. Therefore, it is also recommended to photo or video record all the road sections. This allows more experts to study the most critical sections. Therefore, it might prevent repeated inspections in some cases or even to discover aspects of the infrastructure that were not detect during the initial inspection.

C) Road maintenance Data

Many road authorities and road operators conduct regular automated data collection. The most common of these are the Pavement Management Systems (PMS) which records the road surface characteristics like roughness and wheel ruts. The equipment also usually records crossfall and longitudinal grades as well as curve radius. More safety critical data like road friction is recorded in some maintenance operations. Information is usually stored in short (20 m) intervals that thus provide detailed road information in a computer accessible format.

D) Road inventory software

Over the last years it is being more common that road administrations develop electronic databases with an inventory of the road network. It usually gather all the equipment of the road (signs, road marking, road restraint systems, lighting poles, etc.), its geometry (lane & shoulders type and width, curvature radius, superelevation, longitudinal slope, etc.) and a set of pictures of the road taken regularly along all the road. This type of tool presents many advantages: it is easier and faster to get road parameters, it can be linked with accident databases allowing experts to investigate the relationship of road characteristics with road safety, road layout can be analyzed at critical points or search criteria can be defined in order to identify road sections with parameters under safety thresholds. Whenever this tool is available, it is advisable to use it while applying the Road Safety Index. If that is not the case, usually road administrations should have the information about the road but in other formats (not electronic) and dispersed in different sources. Fortunately, the regional Road Administration of Castilla y León (Spain) did have this tool for its whole road network. Therefore, the RANKERS consortium had the possibility to apply the


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RSI to one of the road sections of this administration. In the Figure 5 the road inventory software for this particular road can be seen.

Figure 5 Castilla y León Regional road network inventory software

E) Complementary data

Although the Road Safety Index pursues a proactive approach it also takes into account the accident data of the road sections it is assessing. It is not used to evaluate the different road infrastructure topics but it is taken into consideration so as to penalize those road sections with a relevant quantity of fatal and serious accidents. It will be presented later in this report how this is introduced in the RSI calculation methodology. There are other types of data that can help to understand some of the road safety problems of road sections. Information related to the traffic flow, its composition, they type of road that it is being analyzed (primary road connecting long distances points or secondary/tertiary road communicating the different population centre within a province). In some cases it might also be good to know if there is any particular road user group over represented so road infrastructure deficiencies detected could be solved taking them into


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account. This can be used to identify issues and priorities actions for particular road users such as vulnerable road users.


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3. RSI road infrastructure topics

This chapter presents the specific topics that the RSI evaluates related to road infrastructure. They have been grouped in six different topics (Road alignment, roadside, junctions, pavement, overtaking and road layout consistency). As it was presented in Chapter 2, all the infrastructure topics are assessed presenting the results in the same marking scale, so they can be compared. For each topic, four grades are available. Specific criteria have been defined for each topic in order to assign each one of the four marks. As a reminder, the four possible marks are as follows (1 being the worst and 4 the best):

1. It is urgent to take remedial measures to solve this infrastructure safety topic. 2. There are deficiencies to be solved in a medium term period. 3. No need of action if maintenance is kept properly. 4. No action is necessary.

In the following subchapters, each one of the road infrastructure topics is presented.

3.1. Road Alignment

Road alignment can be defined as the projection of a road (specially its centre line) on the horizontal and vertical plane1. Therefore, the road alignment may tackle a wide range of parameters. Nevertheless, the RSI just take into consideration those where enough evidence has been found on their influence on road safety. Seven questions have been developed in order to assess the performance of road alignment in road sections. 1 Technical Dictionary of Road Terms (PIARC Technical comité on Terminology and Translation Assistance)


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A) To which interval does the average curvature radius belong to? 1. Average radius smaller than 350 m. Design Speed > 90 km/h 2. Average radius between 350 m – 500 m. Design Speed > 90 km/h 3. Average radius 500 m – 1000 m. Design Speed 70-90 km/h 4. Average radius > 1000 m. Design Speed 80-100 km/h

B) What is the lane width along the road section? Take the minimum value if not constant along the stretch. (LW increase its influence with higher traffic flows, AADT>8020 more influence).

1. LW < 2.75 m. 2. 2.75m < LW ≤ 3 m. 3. 3 m. < LW ≤ 3.25m. 4. LW > 3.25.

C) What is the frequency of sight distance problems along the road section (Due to continuous or punctual obstacles on the roadside or due to confusing crest curves)?

1. Sight distance problems present ≥ 5 times. 2. Sight distance problems present ≥ 3 times. 3. Sight distance problems ≥ 1 time. 4. No sight distance problems within the whole section.

There will be a sight distance problem in the following situations: • Inadequate sight distance on horizontal curves or on crest curves. • If the road gives fake expectations on its alignment. • If it is not possible to guess properly the way ahead on a straight line at level. • If there is an object disturbing the visibility along the roadside.

D) What is the carriageway serviceability index? 1. Very poor pavement and maintenance, rutting, pounding, holes... 2. Presence of rutting, pounding, cracking holes… 3. Slightly deteriorated roads. 4. Good and very good pavements.

E) What is the shoulder serviceability index? Surface type of the shoulder, and shoulder condition. 1. Very poor pavement and maintenance, rutting, pounding, holes... 2. Presence of rutting, pounding, cracking holes, non paved shoulders consisting of gravel, crushed or similar. 3. Paved shoulders deteriorated, maintenance needed. 4. Paved shoulders consisting of bituminous material or concrete with adequate level of maintenance.

F) What is the state of the traffic signing placed on the roadside? 1. Chevron or curve warning missing or ineffective on severe curve. 2. Guideposts or barrier reflectors damaged or missing. 3. Edge lines missing or inadequate. 4. No deficiencies on roadside signing.

G) What is the shoulder width? 1. No shoulder. 2. 40% < difference with reference < 20% 3. Difference with reference < 20% 4. Above reference.

Speed limit Lane width (m) Shoulder width (m) Up to 120 km/h 3.75 2.50 120 km/h - 50 km/h 3.50 1.50 - 1.00* 40 km/h 3.00 1.00

*Depending on the speed and the surface type.


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The literature references used for the above marking criteria are the following ones:

• The handbook of road safety measures [G]

Rune Elvik and Truls Vaa ELSEVIER 2004

• Safety Reviews of Existing Roads [B] - [C] - [F] Quantitative safety assessment methodology Alfonso Montella

• Effects of road geometry and traffic volumes on rural roadway accident rates [D] - [E] Matthew G. Karlaftis, Ioannis Golias Department of Transportation Planning and Engineering, Faculty of Civil Engineering, National Technical University of Athens. Accident Analysis and Prevention 2002

• Rural Road Design-Guide to the Geometric Design of Rural Roads Austroads (1993), Sydney. [G]

• Factors affecting road safety [A] - [B]

Ripcord Iserest Road Infraestructure Safety Protection Sixth framework programme

• Road design and safety [B] - [C] HEDMAN VTI Rapport 351A, pp 225-238, Swedish Road and Traffic Research Institute, Linkoping, 1990, Sweden

• CONTRIBUTIONS FROM SWEDEN AND FINLAND IN RANKERS - RSS Conference paper Thomson, R.; Othman, S.; Lannér, G.; Suhonen, K.; Kelkka, M. & Valtonen, J. (2007), 'The Role of Road Infrastructure on Accident Rate', Proceedings of the International Conference Road Safety and Simulation, 2007 or RANKERS Deliverable D2.1


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3.2. Road junctions – private accesses

Junctions and access to private properties or secondary non paved roads are points where a higher amount of conflicts can be present. Therefore, it is important to analyse how they are designed, signalized among other important factors. The four questions developed for this topic are presented as follows.

A) How many road accesses (NA) or junctions do the section have per km road? • Rural single 1. NA> 16 2. 11 < NA≤ 15 3. 6 < NA ≤ 10 4. 0 ≤ NA ≤ 5 • Rural dual 1. NA > 7 2. 5 < NA ≤ 7 3. 3 < NA ≤ 5 4. 0 ≤ NA ≤ 3

B) Which and how is the access road’s connection to the principal road? 1. 1 < Junction mark ≤ 1.9 2. 2 < Junction mark ≤ 2.9 3. 3 < Junction mark ≤ 3.9= RSI=3 4. Junction mark ≥ 4 Access road’s

connection to the principal road

Accesses inside a curve or close to

crests. Accesses with poor visibility

Road access or junctions in sag

Road accesses or junctions properly

located.

Evaluation 1 2 3 4

No.Accesses

Junction mark = ∑ No. accesses * RSI / Total No. accesses

C) Is there any junction or private access placed right in front of another one? 1. A junction (X or +) or access facing another one near a curve or in a section with poor visibility

for any of the accesses, crossroads. 2. An access or junction (X or +) facing another access with good visibility for both roads. 3. A private access facing another private access. 4. No junction or access facing another access.

One situation is enough to choice a number, between two or more possibilities the worst one will be chosen.

D) What is the most frequent level of signing for the junctions? 1. No signing. 2. Only road marking. 3. Road marking and vertical signalling. 4. Road marking + vertical signalling + central reservation in the main road.


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The following literature references have been used to develop the necessary criteria for the marking criteria of the junctions topic section:

• Access and safety [A] E. Hauer. Draft, April 15, 2001

• Vehicular access to all-purpose. Trunk roads. [B] - [C] The highways agency TD 41/95, The Scottish office development department The Welsh office, The department of the environment for Northern Ireland. • Relationship between accident rate and the number of private access roads

per km road. [A] Muskaug 1985 • The handbook of road safety measures [A] Rune Elvik and Truls Vaa ELSEVIER 2004 • Driveways and Acces points [B] - [C] - [D] Ripcord Iserest, Road Infraestructure Safety Protection. Sixth framework programme • Safety Reviews of Existing Roads [A] Quantitative safety assessment methodology. Alfonso Montella • Effects of road geometry and traffic volumes on rural roadway accident rates

[D] Matthew G. Karlaftis, Ioannis Golias. Department of Transportation Planning and Engineering, Faculty of Civil Engineering, National Technical University of Athens. Accident Analysis and Prevention 2002


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3.3. OVERTAKING

Overtaking manoeuvres are also a complex task that might serious conflicts between road users. This reveals to be even more problematic in single carriageway roads. Therefore, the RSI aims to study with this road infrastructure topic how the road infrastructure contributes to make this type of manoeuvres safer for the road user. For this topic, each of the questions is evaluated for each road direction.

A) Is visibility enough according to road markings of overtaking? 1. Overtaking is allowed in a sharp curve or in a crest. 2. Visibility is not enough to overtake and overtaking is allowed. 3. Visibility is enough to overtake but overtaking is forbidden. 4. Visibility is enough to overtake and overtaking is allowed.

B) Is the available overtaking Road Marking Length (R.M.L) enough to safely overtake taking into consideration the road section design speed?

1. R.M.L < 0,7 R.V (Reference value). 2. 0,7 R.V < R.M.L < 0,9 R.V. 3. 0,9 R.V < R.M.L < 1 R.V. 4. R.M.L > R.V.

Speed (kph) 50 60 70 80 90 100 110 120 130

RML (m) 150 200 250 300 350 400 450 500 550

C) Is overtaking prohibited at anytime within the road section?

1. No (and road layout may cause speeding (or car following) and traffic flow is above 1000). 2. No (and traffic flow is above 1000). 3. Yes (prohibition length is less than 10% length of road section). 4. Yes (prohibition length is above 10% length of road section).

D) Is it permitted to overtake before a junction where left turns are permitted?

1. Yes (even within the junction it is permitted). 2. Yes (less than 150 m. before the junction). 3. Yes (more than 150 m. before the junction). 4. No.

E) Are overtaking vertical signing and road marking visible in the section?

1. Both are not visible. 2. Maintenance status is deficient in both. 3. One of the two categories shows deficiencies. 4. Both are visible and at good maintenance status.


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The following literature references have been used to develop the necessary criteria for the marking criteria of the overtaking topic section

• Overtaking Road-Accidents: Differences in manoeuvre as function of driver age [D] David D. Clarke, Patrick J. Ward and Jean Jones. Department of Psychology, University of Nottingham, NG7 2RD, UK. Accident Analysis and Prevention

• Delineation effects in overtaking lane design [A] Samuel G. Charlton. Traffic and Road Safety Group, Department of Psychology, University of Waikato, Private Bag 3105, Hamilton, New Zealand Transport Engineering Research New Zealand Ltd. PO Box 97846, South Auckland Mail Centre, New Zealand. Accident Analysis and Prevention

• Design Considerations for passing sight distance and passing zones [A] - [B] Yasser Hassan, Lakehead University. A.O. Abd El Halim, Carleton University. Said M. Easa, Lakehead University

• Factors affecting road safety [D] - [E] Ripcord Iserest. Road Infrastructure Safety Protection. Sixth framework programme

• How does it change safety margins if overtaking is prohibited: a pilot study [C] Heikki Summala, Department of Psychology, University of Helsinki, Ritarikatu 5, SF-00170 Helsinki 17, Finland. Accident Analysis and Prevention

• Accidents, overtaking and speed control [D] Ezra Hauer, Technion, Israel Institute of Technology, Haifa, Israel. Accident Analysis and Prevention

• Safety Reviews of Existing Roads [E] Quantitative safety assessment methodology. Alfonso Montella


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3.4. ROADSIDE

In this topic, there is only one “question” that assesses the roadside infrastructure safety protection. Indeed, this question is covering the three main aspects of the roadside that are related to road safety: the distance of the hazard to the carriageway, its crashworthiness and the road layout (straight or curve). Moreover, the calculation method also distinguishes between continuous and discrete hazards in order to calculate the assessment for each road section. The roadside is evaluated through a Risk Index (RI), that is composed of the following terms:

RI = CP*Ce*Ca

Where CP and Ce are coefficients related to the collision with off road obstacle and Ca the coefficient related to the fatal consequence of a collision. CP is the coefficient related to the vertical alignment. The risk to run off the road is considered to be higher in curve than in straight sections. Furthermore, this high risk is also higher when the radius of the curve is reduced. It is higher when the curve is located after a long straight road than in a series of curves (winding section). CP takes the following values: 1 for straight sections and 5 for curves. Ce is the coefficient related to the distance of the hazard to the carriageway (Table 1). The risk of a collision with an off road object is a decreasing function of the distance of the object to the side of the road.

Distance 0 to 1.5m 1.5m to 2.5m 2.5m to 4m Ce 3.5 2 1

Table 1 Ce values related to hazard distance to carriageway

Ca is the coefficient related to the severity of the object. The severity of an object can be defined as the number of killed people for 100 collisions in injury accidents (Table 2).

Type of objects Ca (killed / 100 collisions) Trees 30%

Masonry walls 30% Utility poles and posts 20%

Ditch, cut slopes, fill slopes 10% Table 2 Ca values related to hazard crashworthiness

The above coefficients are calculated for all the roadside objects along the road sections. This evaluation is divided into the continuous and the discrete hazards. Therefore, the calculation of this RI is the sum of both components:


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discreteRIcontinuousRIRI +=

(m)lenght sectionCa) * objnº * Cex *gthcurves_len* (5 Ca) * nº.obj * Cex * engthstraight_l * (1

usRIcontinuo∑+∑

=

∑= )aC*objnº*eC*P(CdiscreteRI

The global mark that the RSI gives for the roadside infrastructure topic depends on the RI value and is defined as follows (Table 3):

RI value RSI roadside mark

RI > 101 1

11 ≤ RI ≤ 100 2

1 ≤ RI ≤ 10 3

RI < 1 4

Table 3 RSI roadside mark definition

The literature references used for the definition of this RI the following:

• Sécurité des Routes et des Rues (Safety on Roads and Streets). SETRA, CETUR, 1992.

• Guide technique traitement des obstacles latéraux sur les routes principales

hors agglomération (Technical Guideline : how to treat roadside objects on rural roads), SETRA, 2002.

• Influence de la distance au bord de chaussée sur les accidents – étude

bibliographique. RISER, Summary of European design guidelines for roadside infrastructure, 2006.

• Influence of the object distance from road edge on traffic accidents – literature

review. CETE Normandie-Centre – août 1995 (CETE Normandie-Centre – August 1995).

• Accidents mortels contre obstacles fixes.

CETE Normandie-Centre, CEESAR, SETRA, mars 1999

• Fatal accidents against fixed obstacles. CETE Normandie-Centre, CEESAR, SETRA, March 1999).


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• Evaluation sur la sécurité de la suppression des plantations.

CETE Normandie-Centre, mars 2000

• Evaluation of the removal of row of trees on safety. CETE Normandie-Centre, March 2000.

• Factors affecting road safety

Ripcord Iserest. Road Infraestructure Safety Protection. Sixth framework programme

• The effects of paved shoulders on accidents on rural highways. K. W. OGDEN Institute of Transport Studies, Department of Civil Engineering, Monash University, Clayton, Victoria 3168, Australia. Accident Analysis and Prevention

• Effects of paved shoulders on accident rates for rural Texas highways

TURNER, D. S. / FAMBRO, D. B. / ROGNESS, R. O. Transportation Research Record 819, pp 30-37, 1981

• The handbook of road safety measures

Rune Elvik and Truls Vaa. ELSEVIER 2004


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3.5. PAVEMENT & SUPERELEVATION

All the maneuvers that vehicles perform are related to the pavement. The pavement must provide a reaction surface for the forces requested by the vehicle in maneuvers, such as turns, braking or acceleration. The pavement status and slopes determines the limits for different forces (longitudinal and/or transversal) that keep the vehicle stable. Therefore it must be taken into consideration This subsection presents the topics that were included in the RSI. Nevertheless, as it will be discussed in Chapter 6, this topic is the one that have presented more difficulties when measuring the different parameters. Some parameters like CRT, that measures the friction that the pavement provides, usually is not provided by road administrations. That is the reason why it has not been included. Moreover, it is not clear what is the best parameter and equipment to measure it guarantying the repetitiveness of the measures and their accuracy at the same time2. The wheel rut is another parameter that might not be easily accessible for road safety research teams, unless the road operator register it and is willing to release that information. Therefore, although it has been included into the issues for this topic, it has not been possible to register it in the application to a real road section of the RSI. This is one the points where more research could be developed in the future years. More knowledge on the relationship between pavement status, friction and safety would be advisable. Moreover, research focused on parameters easier to be registered when performing road safety inspections and their relationship to road safety would be also beneficial. The following are the topics that have been developed in order to theoretically evaluate the influence of road infrastructure related to pavement and superelevation with road safety along the road sections.

2 HERMES Final Report (Harmonization of European Routine and research Measuring Equipment for Skid Resistance)


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The literature references used for this section are the following ones:

• Shoulders at Superelevated Curves [A] 3C-3 Design Manual, Chapter 3 Cross Sections. Iowa Department of Transportation Office of Design

• Superelevation [A]

2A-2 Design Manual, Chapter 2 Alignments. Iowa Department of Transportation Office of Design

• Road curve superelevation design: Current practices and proposed approach

[A] Road & Transport Research, Jun 1999 by Kanellaidis, G

• Vägverket Publication 2004 [C] • CONTRIBUTIONS FROM SWEDEN AND FINLAND IN RANKERS - RSS

Conference paper Thomson, R.; Othman, S.; Lannér, G.; Suhonen, K.; Kelkka, M. & Valtonen, J. (2007), 'The Role of Road Infrastructure on Accident Rate', Proceedings of the International Conference Road Safety and Simulation, 2007 or RANKERS Deliverable D2.1

A) Which is the road curve super elevation design (taking into consideration weather conditions and type of traffic of the section?

5. emax > 0.12 Traffic with slow moving vehicles and ice or snow may be present during the year. 6. emax> 0.10 Traffic with slow moving vehicles and ice or snow may be present during the year. 7. 0.08 < emax ≤ 0.10 8. 0.06 < emax ≤ 0.08 (mountains 0.10-0.12 may be acceptable).

B) Wheel rut, WR (mm).

1. WR ≥ 20 2. 10 ≤ WR < 20 3. 3 ≤ WR < 10 4. WR < 3

C) Unevenness 5.

i. Fairly deep, > 5 cm, long bowled shape unevenness most likely due to road settlement.

ii. Bump and hollow, > 5 cm, due to for example frost heave damage, pavement damage and conduit beats.

6. Uneveness > 2,5 cm. 7. 1,5 cm ≤ Uneveness < 2,5 cm. 8. . Uneveness < 1,5 cm


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3.6. CONSISTENCY

The previous five road infrastructure shows the great variety of components of a road. It is important not only that each one of them is designed properly safe but also that the possible interactions between them and its influence in safety is also considered. That is the objective of this topic. It aims at analyzing how the relationship between some road layout parameters may influence in road safety. Three aspects have been considered the most relevant for the scope of this index: the unexpected events that may require of the driver reaction, the consistency between road markings and vertical signs and relation between the radius of curvature of consecutive curves.

A) Are there unexpected features requiring driver action? 1. Very severe curve, realignment needed. 2. Roundabout or junction not expected. 3. There is a section bigger than 2000 m without changes. 4. No unexpected features. (Transition curves, signing properly placed, etc.).

B) Are road markings and signals consistent in the section? 1. Road markings and/or signals missing. 2. Road markings and/or signals in poor state. 3. Road markings and/or signals not visible or un-properly placed. 4. Road markings and signals in good conditions and properly placed.

C) Which is the coefficient between the radii of the current curve and the curve before? 1. Areas either out of the central area, or out of the possible area. Transitions from a bigger radius

into a smaller radius. 2. Areas close to the possible areas. 3. Areas immediately above and under the central area – Acceptable 4. Central area-Good design. Transitions from a smaller radius into a bigger radius.

Ratio of consecutive curves, Lippold (1997)

D) Which is the number of unexpected curves (curve combinations with reducing curve radii) per km road?

1. More than 2 curves per km. 2. From 1,34-2 curves per km. 3. From 0,4 to -1,33 curves per km. 4. 0 curves per km.


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The literature references used for this topic in the definition of the marking criteria are the following ones:

• Safety Reviews of Existing Roads [A] - [B] Quantitative safety assessment methodology. Alfonso Montella

• Factors affecting road safety [C]

Ripcord Iserest. Road Infraestructure Safety Protection. Sixth framework programme • Effects of road geometry and traffic volumes on rural roadway accident rates

[D] Matthew G. Karlaftis, Ioannis Golias. Department of Transportation Planning and Engineering, Faculty of Civil Engineering, National Technical University of Athens. Accident Analysis and Prevention 2002

• SAFESTAR Safety Standards for Road Design and Redesign [A]

Final Report November 2002

• The handbook of road safety measures [D] Rune Elvik and Truls Vaa. ELSEVIER 2004


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4. RSI Procedure of application

The RSI methodology has been developed and the road infrastructure topics that it tackles have been presented in Chapter 3. This chapter summarizes the process to be followed in order to apply the RSI.

4.1. Definition of the road sections

Ideally, the RSI should be applied to a road network or to a group of roads. This may allow investigating which sections of the road network need of improvements and also what type of improvements. Nevertheless, the RSI can also be applied to a single road. The RSI user should divide the roads where the RSI is to be applied in as many sections as necessary with a road length section of 1,5 – 2 km. The RSI will be applied independently to each one of them.

4.2. Collection of data

Once the road sections are defined, the next step is to prepare the necessary sources of data in order to apply the RSI.

• If available, the road network inventory software should be prepared to be used by the road safety analyst. A detailed review of the parameters it includes may help to avoid some of the road safety inspections. If this tool is not available, the road safety analyst should look for the available databases covering the road design & equipment parameters or will prepare a checklist to be completed when developing the road safety inspections in order to measure the necessary parameters.

• The road sections have to be video recorded. The road analyst will take benefit of the necessary driving visit to the roads to assess which road sections deserve of a specific road safety inspection.

• Other complementary information has also to be collated: accident data, traffic flow, identify the type of road network that each road belongs to, etc.

• Any additional information related to the road might be useful. For example, knowing the typical type of traffic (local, long distance, etc.) or the presence of particular


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groups of users may help the road safety analyst identifying the potential problems of the road infrastructure deficiencies detected by the RSI.

4.3. Application of the RSI to each road section

The next step is to apply the RSI to each section. This means analysing the necessary data in order to answer all the questions related to each road infrastructure topic that have been presented in Chapter 3. As all the answers are expressed in a numeric scale, ranging from 1 to 4, the results can be compared within each road section. Within each category, the average mark has also to be calculated in order to give a global evaluation of each specific road infrastructure issue. After this process has been concluded, for each road section the road safety analyst should be able to construct a table like Table 4, which is an example of a fulfilled in tabled of a road section after applying the RSI. Stretch length 1,6 km. AADT 25520 Accident Data

Initial milestone 25,36 Type of road

Single Carriageway

Double carriageway

Total Accidents

Injury accidents

F & S accidents Fatalities

Final milestone 26,96 Type of road network

Primary

Secondary

Tertiary

1 1 0 0

OVERTAKING ROAD ALIGNMENT

ROAD ACCESSES ↑ ↓

ROADSIDE PAVEMENT & SUPERELEVATION CONSISTENCY

A) 4 A) 4 A) 2 A) 2 A) 4 A) 4

B) 4 B) 2 B) 1 B) 1 B) N/A B) 2

C) 3 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 3

E) 4 E) 4 E) 4

F) 4

G) 3

RI 2

3.72 3 2.75 2.75 2 4 3.25

Table 4 RSI application results to a road section

This table represents the result of the application of the RSI to a road section. It allows identifying the different safety performance for each road infrastructure topic in the road section. For instance, in this example attention should be paid to the Overtaking section, as it takes one of the lowest score. Moreover, looking at the different questions for this topic, question B which is


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related to the road marking length for overtaking manoeuvres gets the lowest score. Therefore, this issue should be revised in this section. The roadside topic should also be reviewed carefully as it gets the lowest average score. This means that more protection is necessary related to roadside hazards, that might be dangerous in the event of a run – off accident in this road section.

4.4. Accident correction factors for average marks

Until this point, the accident data that is gathered for the RSI has not been used. This is mainly because the approach of the RSI should be proactive, meaning that it should not be addressing only road sections with previous accidents. Nevertheless, for those sections where there have been a significant number of serious accidents, this might mean that they need to be prioritized when distributing investments in safe infrastructure. In order to combine both aspects, a procedure has been developed in order to modify the average mark for each road infrastructure topic according to the historic accident data. The objective is to decrease the marks for those sections where the accident data is significantly higher than the others. Nevertheless, the RSI can be applied first without these correction factors if the road safety analyst deems it appropriate. The procedure is applied in two steps. The first one is aimed at calculating the Correction Factor (CF) for each road section and the second one looks for the road sections to which it should be applied. This means that there could be road sections where there is no need to apply a Correction Factor.

4.4.1. Correction Factors calculation

The Correction Factor to be applied is calculated based in two different parameters:

• The number of road sections of the same road where the RSI is applied (N). • The sum of fatal and serious accidents for each road section (FSi)

For each road section the CF is defined as indicated in Table 5:


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CF (FSi/N) < 0,5 0,15

0,5 ≤ (FSi/N) < 1 0,30 1 ≤ (FSi/N) < 2 0,7 2 ≤ (FSi/N) < 3 1

(FSi/N) ≥ 3 Table 5 CF calculation for each road section

Then, the second step is to decide to which road sections it is necessary to apply the CFs calculated in the first step. The criteria to be applied is based in the following parameter:

NFS

A i∑=

Equation 1 Parameter for determination of road sections where CF is necessary

• If FSi ≤ A, then it is not necessary to apply the CF in road section i. • If A < FSi ≤ 2*A, then the CF calculated needs to be applied in road section i. • If FSi > 2*A, then 2*CF is applied to road section i.

Once this process has been applied to all the road sections where the RSI is applied, the road operator will be able to identify the road sections where it is necessary to enhance road infrastructure together with a specification of the topics that need to be addressed. Those sections where due to the historic accident data the modifications are critical will be also identified.


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5. Application of the RSI to a real road

In order to test the index developed, it has been applied to a real road. This has allowed identifying the possibilities of the index as well as the main difficulties that a road safety analyst may encounter when applying it. A 44 km component of a single carriageway road was chosen for the application of the index. It divided in 17 road sections of approximately the same length, ranging from 1,75 to 2,15 km. This road might be considered as a secondary road within the regional road network and the typical displacements it covers can be considered as short – medium length trips (no longer than 100 km.). During the period 2004 – 2006, there were 8 fatal or serious accidents with one fatality in this road. The procedure explained in the previous chapter was applied to those road sections. In this case, and due to the collaboration of the Regional Road Administration of Castilla y León, the road inventory software was available for this application. Road safety experts developed visits to the road sections, and the whole road was video recorded so as to facilitate the analysis at the office. In Annex I, all tables with the results of the application of the RSI are included. In the following subsections the main results for each road infrastructure topic are presented together with some examples of pictures that may contribute to illustrate each result.

5.1. Road Alignment

The application of the RSI to this real road section has shown that in terms of road alignment there are no relevant problems in all sections. The marks for each road section related to this topic are presented in Figure 6. The lowest score is 3 for the road section 17 and most of the road sections remain above 3,5. The issues that are mainly related to the lowest scores are the status of the pavement in some short lengths of the road sections, this is recurring problem in the road sections but just in some discrete locations. One example of this, related to section 14 is shown in Figure 7


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ROAD ALIGNMENT

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

Mar

k

Figure 6 Road Alignment RSI marks by road section

Figure 7 Poor pavement status in road section 14

Moreover, it is considered as a positive result that along the entire road, the marks for this road infrastructure topic remain stable above 3. This means (within this subject area) the driver should not find important differences between consecutive road sections.


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5.2. Road Accesses

In this road infrastructure topic the results do not seem to be as homogenous as for the road alignment topic and can be seen in Figure 8.

ROAD ACCESSES

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

mar

k

Figure 8 Road Accesses RSI marks by road section

There are some important points to be remarked:

• The lowest score was 2,37 and the highest 3,7. • There are relevant variations in the marks between consecutive road sections. • As there are various road sections with marks between 3 and 2, any future maintenance

program developed in this road should consider actuations on this topic. • As it can be seen in Figure 9, there are two main problems found related with this topic:

the excessive number of consecutive accesses on the road and in some cases the position of accesses in both sides of the road one in front of the other, multiplying the number of potential conflicts.


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Figure 9 Road Accesses deficiencies in road sections 4 & 6


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5.3. Overtaking

In Figure 10 the result for the overtaking topic are shown.

OVERTAKING ↑

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

mar

k

OVERTAKING ↓

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

mar

k

Overtaking Comparison

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

mar

l

OVERTAKING ↑OVERTAKING ↓

Figure 10 Overtaking marks by road section


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For this topic, it was deemed appropriate to evaluate separately by both directions as the visibility problems might be different. In fact, for some road sections the marks are different for each direction, though they and sometimes they differ greatly as it is the case of road section 14. The more relevant comments are as follows:

• In both directions, the general assessment is positive. This means that road infrastructure do not promote conflicts when road users need to perform overtaking manoeuvres.

• Nevertheless, there are some road sections, in both directions, with a score lower than 3. Again, in future maintenance programs, attention should be paid in order to develop some countermeasures that help to enhance the performance of these road sections. For example, road markings in Figure 11 allow overtaking manoeuvres when there is a crest that obstruct the visibility of oncoming vehicles.

• As expected when the structures were planned for this topic, some road sections will have marks depending on the road direction.

Figure 11 Overtaking allowed in section 8 when there is not enough visibility


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5.4. Roadside

In this case, the RSI shows that the roadside do not offer such a good level of safety as the previous road infrastructure topics. Apart from road section 1, where the roadside marking is the highest, the other ones are always equal or below 3, and in some cases even below 2. This means that there are some road sections where it is necessary to correct some deficiencies. Indeed, in this road, one of the fatal accidents occurred last year was related with the roadside equipment.

ROADSIDE

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

mar

k

Figure 12 Roadside marks by road section

The main issues to be mentioned are the following ones:

• There have been found several concrete culvert devices placed just after the shoulder with a geometry that do not consider safety at all. They are not safe in case that a road user leaves the road and impacts against them. One of those was involved in the fatal accident mentioned above (Figure 13).

• In some road sections there are unprotected punctual obstacles like trees too close to the road carriageway (Figure 13).

• The geometry of the ditch is some stretches might be softened or protected with a road restraint system.


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Figure 13 Tree too to close to the carriageway (road section 3) & concrete culvert (road section 4)


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5.5. Pavement & Superelevation

As it will be explained in the next chapter, this road infrastructure item has been the most difficult to assess due to the fact that it was impossible to answer some of the questions included in the index with the available information. Therefore, although the general assessment for this topic in this road is quite positive, it could be better defined with more information regarding some parameters like friction coefficients for example.

PAVEMENT & SUPERLEVATION

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

Mar

k

Figure 14 Pavement & Superelevation marks by road section

Figure 14 shows how the road evaluation is homogeneous for this topic. All marks are equal or above 3, what means that there are no major deficiencies with the pavement design. The only issue that should be mentioned already appeared when we studied the pavement from the point of view of the road alignment and found in road section 14 some specific stretches where the pavement status should be improved when carrying out future maintenance programs (Figure 7).

5.6. Consistency

As it can be observed in Figure 15, the consistency of this road is homogeneous and remains along the whole road at good safety levels. In some transitions between road sections, the marks decrease, always within safe margins, mainly due that the transition from long straight sections to a more sinuous layout could still be improved. Nevertheless, it is considered for this road that this could constitute a safety problem that needs to be tackled with priority.


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CONSISTENCY

0

1

2

3

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Road Section

RSI

mar

k

Figure 15 Consistency marks by road section

5.7. Identification of road infrastructure safety priorities in the road

In the previous subsections each road infrastructure topic has been analysed in order to detect the main issues. Nevertheless, from the point of view of a road administrator it could be interesting to analyse the results from the point of view of Table 6. This is to detect what road sections were in need of road infrastructure safety improvement and what parts of the road infrastructure should be improved. The main conclusions are the following ones:

• Pavement and Consistency do not need to be tackled with priority. Only some specific points should be considered in future periodic maintenance programmes. They have been mentioned in their correspondent subsections. The same can be stated for Road Alignment as only the road section 17 deserves some priority.

• The frequency and location of accesses should be reviewed in sections 3, 4, 6 ,7, 8 & 14. • The coordination between overtaking road marking and available visibility should be

reviewed in sections 2, 7, 8, 9 and 14 taking into consideration the road direction. • Roadside infrastructure devices should be revised urgently in sections 2 and 8. They get

the lowest score of the study. Moreover, sections 4, 6, 7, 9, 10, 14 and 17 needs to be also reviewed with a lower priority than the above mentioned.

• Sections 7 and 8 are the ones with lowest scores and it could be advisable to develop a more detailed review and improvement of their road infrastructure.


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S1

S2

S3

S4

S5

S6

S7

S8

S9

S10

S11

S12

S13

S14

S15

S16

S17

Table 6 RSI marks of the road by road section and road infrastructure topic

ROAD ALIGNMENT: lanes & shoulder width, curvature radius, visibility, etc.

ROADSIDE: geometry, presence of obstacles and distance to the carriageway, safety equipment, etc.

JUNCTIONS: nº of junctions present, nº of private accesses and their coordination, level of signing at intersections, etc.

PAVEMENT: assessment of the pavement status, superelevation coordination and transition in curves, etc.

OVERTAKING: coherence between road marking – vertical signs, available visibility for overtaking manoeuvres.

ROAD LAYOUT CONSISTENCY: curvature of consecutive curves, drivers’ perception, etc.

Figure 16 RSI road infrastructure topics


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6. Main difficulties and research needs

Due to the innovative approach followed when developing and applying the Road Safety Index, the research team has faced some difficulties that, at the same time, have provided the identification of some research needs that should be further explored in the future. The problems have been mainly related to the availability of data to assess some issues in each topic. Even when no data has been available for the whole road, and is considered to be a common situation in all roads, these issues have been kept in the RSI structure because they are considered relevant to the relationship between road infrastructure and safety. This could be solved in the future by two different ways:

• Developing systems or methodologies that allow safety research teams to measure these parameters along road sections at a reasonable time cost.

• Performing research analysis relationship between the values of these variables with other ones that are easily measurable.

The data that has not been available for this application and is considered not to be usually available for roads are the following:

• Pavement & Superelevation: wheel rut and unevenness data have not been available for the application of the RSI in Spain. These data items are often available and were studied in WP2. Further analysis is needed particularly when the RSI is to be applied to motorways. Often only the low speed lane is measured in multilane facilities. Pavement friction has not even been included in the RSI structure. This is not because it is not relevant for safety from a road infrastructure point of view. Nevertheless, it was not possible to obtain SFC (Side Friction Coefficient) data from road operators in the RANKERS project. Moreover, as it is further explained in the final report of the HERMES3 project, it is not yet clear what device should be used to measure this parameter on the roads that is able to assure measures repetitiveness.

• Road Accesses: question D, that refers to the situation where left turns are allowed from a private access and at the same time overtaking is allowed in the principal road have been difficult to evaluate. The fact is that most of those accesses are not considered in the road layout, and therefore they are not signalised to the users of the main road. A common criteria should be developed to tackle this issue.

The RSI could be improved in the future if there is available data regarding the above issues. It could also be refined by its application to a larger and wider set of roads.

3 http://www.fehrl.org/?m=103


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7. Conclusions

One of the two basic objectives of the RANKERS project was to develop an index able to assess the road infrastructure along road networks. This should allow identifying the most critical sections related to road infrastructure safety and the aspects of the road infrastructure that should be improved. The realization of this objective has been presented in this report, showing the structure, methodology, applicability and difficulties of this innovative tool for road administrators and operators. It will allow experts to detect locations where they should invest resources and what component needs to be addressed to improve safety. This is the first European road safety index that analyses in depth the different aspects of the road infrastructure and their influence on road safety. The collaboration of public administrations, like the Regional Administration of Castilla y León (Spain) in the development and application of the index has been crucial. The research team deems it necessary to get the motivation and involvement of road administrations in the application of the index. They get a proactive approach for safety and road infrastructure and this will provide a safety benefit at medium – long term when new roads will be designed. Nevertheless, it must be mentioned that it is not to applied as a standalone tool in safety. Each road is different and has its own socio - cultural and demographic aspects. The more complementary information that is available the better the safety assessment of road networks the RSI will produce. That is why this research team recommends using the RSI together with a multidisciplinary team on road safety. As it is usual in all innovative research, some difficulties have been detected when developing this index. This research team deems it advisable to allocate more research efforts in the following topics that might help in the future to improve safety be refining tools like the RSI:

• Information related to how infrastructure items interact with each other. Obviously items like road friction affects speeds in curves. Additionally how the driver interprets the road must be better understood so that consistency concepts like unexpected curves can be better quantified. Information is available that describes how many of the RSI parameters affect safety. However we are still far from having a complete understanding on how to quantify each contribution.

• The main efforts of the presented RSI have been allocated to single carriageway roads although it can be potentially applied to double carriageway roads with some modifications. This has been mainly due to the fact that these roads are not so deeply


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considered by other existing indexes while they gather a relevant figure of the fatal and serious accidents. Nevertheless, it would be advisable to extent the application of this index to a larger number of different roads in order to develop some improvements or refinements.

The index has shown to be useful when applied to a real road. Those road sections with deficiencies have been identified and a criterion for the urgency of the necessary improvements was also established. At last, the result that this report represents is in line with the approach of the European Directive on Road Infrastructure Safety Management that has recently been approved (http://ec.europa.eu/transport/roadsafety/infrastructure/safety_mgnt_en.htm).


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I. RSI application results

I.1 Road Section 1 Stretch length 1,974 AADT 2552 Accident Data

Initial milestone 11,341 Type of road Single

Carriageway Double

carriageway Injury accidents F & S accidents Fatalities

Final milestone 13,315 Type of road network Primary Secondary Tertiary 0 0 0

OVERTAKING

ROAD ALIGNMENT ROAD

ACCESSES ↑ ↓


A) 4 A) 4 A) 2 A) 2 A) 4 A) 4

B) 4 B) 4 B) 4 B) 4 B) N/A B) 4

C) 4 C) 2 C) 4 C) 4 C) N/A C) N/A

D) 4 D) 3 D) 4 D) 4 D) 4

E) 4 E) 4 E) 4

F) 4

G) 4

RI 4

RSI 4 3,25 3,6 3,6 4 4 4

RSI - FC 4 3,25 3,6 3,6 4 4 4

Table 7 RSI results for road section 1


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Carriageway Double



OVERTAKING

ROAD ALIGNMENT ROAD

ACCESSES ↑ ↓


A) 4 A) 4 A) 2 A) 4 A) 4 A) 4

B) 4 B) 3 B) 1 B) 1 B) N/A B) 4

C) 4 C) 4 C) 4 C) 4 C) N/A C) 4

D) 4 D) 4 D) 4 D) 4 D) 4

E) 4 E) 4 E) 4

F) 4

G)

RI 2

RSI 3,86 3,75 3 3,4 2 4 4

RSI - FC 3,56 3,45 2,7 3,1 1,7 3,7 3,7



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Carriageway Double



OVERTAKING

ROAD ALIGNMENT ROAD

ACCESSES ↑ ↓


A) 4 A) 4 A) 2 A) 2 A) 3 A) 4

B) 4 B) 1 B) 4 B) 4 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) 3 D) 4 D) 4 D) 4

E) 4 E) 4 E) 4

F) 4

G) 3

RI 3

RSI 3,86 2,75 3,6 3,6 3 3 4

RSI - FC 3,86 2,75 3,6 3,6 3 3 4



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Carriageway Double


Final milestone 21 Type of road network Primary Secondary Tertiary 2 0 0

OVERTAKING

ROAD ALIGNMENT ROAD

ACCESSES ↑ ↓


A) 4 A) 3 A) 2 A) 2 A) 4 A) 4

B) 4 B) 1 B) 4 B) 4 B) N/A B) 4

C) 4 C) 3 C) 2 C) 2 C) N/A C) 4

D) 4 D) N/A D) 4 D) 4 D) 4

E) 4 E) 4 E) 4

F) 4

G) 3

RI 2

RSI 3,86 2,33 3,2 3,2 2 4 4

RSI - FC 3,86 2,33 3,2 3,2 2 4 4



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Initial milestone 21 Type of road Single

Carriageway Double



OVERTAKING

ROAD ALIGNMENT ROAD

ACCESSES ↑ ↓


A) 4 A) 4 A) 2 A) 2 A) 4 A) 4

B) 4 B) 2 B) 4 B) 4 B) N/A B) 4

C) 4 C) 3 C) 3 C) 3 C) N/A C) 4

D) 4 D) N/A D) 4 D) 4 D) 1

E) 4 E) 4 E) 4

F) 4

G) 3

RI 3

RSI 3,86 3 3,8 3,8 3 4 3,25

RSI - FC 3,86 3 3,8 3,8 3 4 3,25



D4.2 47 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT ROAD

ACCESSES ↑ ↓


A) 4 A) 4 A) 4 A) 4 A) 4 A) 4

B) 4 B) 2 B) 4 B) 4 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) 4 D) 4 D) 4

E) 4 E) 4 E) 4

F) 4

G) 4

RI 3

RSI 4 3 4 4 3 4 4

RSI - FC 3,7 2,7 3,7 3,7 2,7 3,7 3,7



D4.2 48 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES

↑ ↓ ROADSIDE PAVEMENT &

SUPERELEVATION CONSISTENCY

A) 4 A) 3 A) 1 A) 1 A) 4 A) 4

B) 4 B) 2 B) 4 B) 4 B) N/A B) 4

C) 3 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 4

E) 4 E) 4 E) 4

F) 4

G) 3

RI 2

RSI 3,71 2,67 2,67 2,67 2 4 4

RSI - FC 3,71 2,67 2,67 2,67 2 4 4



D4.2 49 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 3 A) 1 A) 1 A) 4 A) 4

B) 4 B) 2 B) 4 B) 4 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 3

E) 4 E) 4 E) 4

F) 4

G) 3

RI 2

RSI 3,86 2,67 3,25 3,25 2 4 3,75

RSI - FC 3,56 2,37 2,95 2,95 1,7 3,7 3,45



D4.2 50 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 2 A) 2 A) 4 A) 4

B) 4 B) 2 B) 1 B) 1 B) N/A B) 2

C) 3 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 3

E) 4 E) 4 E) 4

F) 4

G) 3

RI 2

RSI 3,72 3 2,75 2,75 2 4 3,25

RSI - FC 3,72 3 2,75 2,75 2 4 3,25



D4.2 51 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 4 A) 4 A) 4 A) 4

B) 4 B) 3 B) 4 B) 3 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 4

E) 4 E) 4 E) 4

F) 4

G) 3

RI 3

RSI 3,86 3,33 4 3,8 3 4 4

RSI - FC 3,56 3,03 3,7 3,5 2,7 3,7 3,7



D4.2 52 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 4 A) 4 A) 4 A) 4

B) 4 B) 3 B) 4 B) 3 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 4

E) 4 E) 4 E) 4

F) 4

G) 3

RI 3

RSI 3,86 3,33 4 3,75 3 4 4

RSI - FC 3,86 3,33 4 3,75 3 4 4



D4.2 53 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 4 A) 4 A) 4 A) 4

B) 4 B) 3 B) 4 B) 4 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 4

E) 4 E) 4 E) 4

F) 4

G) 3

RI 3

RSI 3,86 3,33 3,6 3,6 3 4 4

RSI - FC 3,86 3,33 3,6 3,6 3 4 4



D4.2 54 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 4 A) 4 A) 4 A) 4

B) 4 B) 4 B) 2 B) 4 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 4 D) N/A D) N/A D) N/A D) 4

E) 4 E) 4 E) 4

F) 4

G) 3

RI 3

RSI 3,86 3,67 3,5 4 3 4 4

RSI - FC 3,86 3,67 3,5 4 3 4 4



D4.2 55 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 3 A) 4 A) 4 A) 4 A) 4

B) 4 B) 3 B) 4 B) 1 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 3 D) N/A D) N/A D) N/A D) 4

E) 3 E) 4 E) 4

F) 4

G) 2

RI 3

RSI 3,46 3 4 3,25 3 4 4

RSI - FC 3,16 2,7 3,7 2,95 2,7 3,7 3,7



D4.2 56 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 4 A) 4 A) 4 A) 3

B) 4 B) 3 B) 4 B) 3 B) N/A B) 4

C) 4 C) 3 C) 4 C) 4 C) N/A C) 4

D) 3 D) N/A D) N/A D) N/A D) 4

E) 3 E) 4 E) 4

F) 4

G) 2

RI 3

RSI 3,43 3,33 4 3,75 3 4 3,75

RSI - FC 3,43 3,33 4 3,75 3 4 3,75



D4.2 57 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 4 A) 2 A) 4 A) 3

B) 4 B) 4 B) 4 B) 4 B) N/A B) 2

C) 4 C) 3 C) 2 C) 2 C) N/A C) 4

D) 2 D) N/A D) N/A D) N/A D) 4

E) 3 E) N/A E) N/A

F) 3

G) 2

RI 3

RSI 3,43 3,67 3,33 3,33 3 4 3,25

RSI - FC 3,43 3,67 3,33 3,33 3 4 3,25



D4.2 58 / 58



Carriageway Double



OVERTAKING

ROAD ALIGNMENT

ROAD ACCESSES



A) 4 A) 4 A) 4 A) 4 A) 4 A) 3

B) 4 B) 4 B) 4 B) 4 B) N/A B) 3

C) 4 C) N/A C) 4 C) 4 C) N/A C) 4

D) 3 D) N/A D) N/A D) N/A D) 4

E) 3 E) 4 E) 4

F) 3

G) 2

RI 3

RSI 3,29 4 4 4 3 4 3,5

RSI - FC 2,99 3,7 3,7 3,7 2,7 3,7 3,2


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