VTI k onferens 18A, 2001 Proceedings of the Conference

VTI k onferens 18A, 2001 Proceedings of the Conference

Road Safety on Three Continents

International Conference in Moscow, Russia,

19–21 September, 2001

VTI konferens 18A · 2001

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Traffic Safety on Three Continents

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VTI konferens 18A

Preface

The international conference Traffic Safety on Three Continents in Moscow, 19–21 September 2001, was organised jointly by the Swedish National Road and Transport Research Institute (VTI), the State Scientific and Research Institute of Motor Transport in Moscow (NIIAT), U.S. Transportation Research Board (TRB), the South African Council for Scientific Industrial Research (CSIR), South Africa, and Forum of European Road Safety Research Institutes (FERSI).

The Moscow conference was the 12

in this conference series. Earlier annual conferences have been held in Sweden, Germany, France, the United Kingdom, the Netherlands, Czech Republic, Portugal and South Africa.

Conference sessions covered a number of road traffic safety issues:

- Advanced road safety technology - Road safety audits

- Policy and programmes - Traffic engineering

- Vulnerable and old road users - Alcohol, drugs and enforcement - Human performance and education - Behaviour and attention

- Data and models - Cost and environment

- Speed and speed management

Linköping in November 2001

CONTENTS

Session 1. ROAD SAFETY ON DIFFERENT CONTINENTS

National road safety strategy in Ghana

Relationship between accidents and geometric characteristics for four lanes median separated roads

Ciro Caliendo, University of Naples, Italy

The main problems of road safety in St. Petersburg and ways of their solution

Safer guardrail to bridge rail transitions

Charles F McDevitt, Federal Highway Administration, USA

Session 2. ADVANCED TECHNOLOGY

Acceptance of advanced assistance systems by Czech drivers

Active safety of trucks and road trains with wide base single tyres instead of twin tyres

Implementaion of a cellular phone terminal in a transportation processes as a function of traffic safety improvement

Martin Lipicnik, University of Maribor, Slovenia

Improving safety at road works. How far can you go?

Michel M. Kusters, Traffic Research Center, The Netherlands

Utilizing road weather information system (RWIS) data to improve response to adverse weather conditions

Jodi L. Carson, Montana State University, USA

Session 3. AUDITS AND OTHER METHODS

Road safety audits of existing roads

Katrine A. Langer, Danish Road Directorate, Denmark

Environment, behaviour patterns and road safety

A study of safety effects of road infrastructure improvements, in Israeli conditions

A new methodology of accident analysis using safety indicators related to functional road classes

Luisa Zavanella/G.Martineli, University of Brescia, Italy

N = 1: Independent investigation into single accidents,added value for road safety research

Theresa van der Velden, Duch Transport Safety Board, The Netherlands

Session 4. POLICY AND PROGRAMMES

The first federal program for ensuring road traffic safety in Russia (some results of practical realization)

Valentin V. Silyanov, Road Traffic Safety Scientific Council, Russia

Strategy of the implementation of a national traffic safety porgramme - the Austrian intention

Wolfgang J. Berger, Institute for Transport Studies, University Bodenkultur, Vienna, Austria

Action plans for traffic safety – New Danish examples

Anne Eriksson, Danish Road Directorate, Denmark

A statistical analyses of traffic fatality reductions in developed countries: the role of medical technology

Robert B Noland, Imperial College of Science, UK

Traffic safety comparison of some post-socialist and high-developed countries

Opening of borders as a challenge to traffic safety work

Road Safety Problems in Greece

Anastasios Tsagklas, Ministry of PublicWorks, Greece

Assessment of effectiveness of active speed warning signs – use of inductive loop data or empirical

Thorsten Kathmann, Institut für Strassenwesen (isac) der RWTH Aachen, Germany

Similarities and dissimilarities of road accident patterns for chosen types of urban intersections

Marzena Nowakowska, University of Technology, Poland

The imagination of road users about traffic accident - comparative research in Poland and Russia

Tadeusz Rotter, Transport Psychology Unit, Jagiellonian University, Poland

Shared Responsibility For Road Safety

Matts-Åke Belin, Swedish National Road Administration, Sweden

Children in cars. Experiences from successful prevention and development of mortality and morbidity among Swedish children in road traffic accidents during the 1980s and 1990s

Robert Ekman, Karolinska Institutet, Sweden

Road safety at the start of the third millennium

Making the network safer – the highways agency strategic safety plan

Session 5. TRAFFIC ENGINEERING

Older driver highway design: The development of a handbook and training workshop to design safe road environments for older drivers

Jennie Oxley, Monash University Australia

Could adherence and road geometry be used to identify the areas of risks?

Michel Gothie, CETE of Lyon, France

Severity of run-off-crashes whether motorways hard shoulders are equipped with a guardrail or not

Jean-Louis Martin, INRETS, France

Accident detection through digital video analysis as an option to increase tunnel safety

Motorway Control Systems at highly-stressed Motorways in a Metropolitan Area

Koblenz, Germany

Roundabouts in Slovenia – ten years experiences

2+1 - Roads with cable barriers- Safety and traffic performance results

The new approach to traffic planning and street design

Road Safety and traffic operational benefits of offset T-intersections

The policy of state regulation in the sub system ‘state control of the vehicle condition’

Rusakov V.Z., SRSUES, Russia

Differences in Traffic Signs’ Recognition between Drivers of Different Nations

University of Bahrain, Bahrain

Session 6. VULNERABLE AND OLD ROAD USERS

Age-related functional impairments and the impact on the ability to cross roads safely

Development of a national licence assessment program for older drivers in Australasia

Bus and coach passenger casualties in non-collision incidents

Investigation of accident involving vulnerable road users in Greek urban areas

Modeling pedestrians´ crossing behaviour: Some empirical evidence

Session 7. ALCOHOL, DRUGS AND ENFORCEMENT

Alcohol, illegal drugs and driving in Belgium

Automatic speed control – The Danish pilot project

Reduction of BAC limit from 0.05 to 0.02 percent in Norway – effects on driver knowledge and behavior - some preliminary results

Terje Assum, TÖI, Norway

Session 8. HUMAN PERFORMANCE AND EDUCATION

Identifying subgroups of road users for countermeasure development: Two Australian examples

Teresa M. Senserrick, Monash University, Australia

Attitudes, risk behaviour and accident involvement among Norwegian drivers

Attitudes towards traffic safety, risk perception and behaviour among young drivers and their passengers

Torbjörn Rundmo, Norwegian University, Norway

The influence of sight distance for the speed of vehicles and road safety – Inquiry and comparison in different European countries

Klaus Habermehl, Fachhochschule Darmstadt, Germany

The TRAINER project – development of a new cost-effective Pan-European driver training methodology and how to evaluate it

Torbjörn Falkmer, VTI, Sweden

The effects of diabetes and low blood sugar levels on driving behaviour:comparison of diabetics and non-diabetics.

Marike H. Martens, TNO Human Factors, The Netherlands

The effect of traffic flow improvements on driver attitudes towards pavement markings and other traffic control devices, and pedestrian safety

David Robinson, Fayetteville State University, USA

Session 9. BEHAVIOUR AND ATTENTION

Fatigue of professional truck drivers in simulated driving: A preliminary study

Dealing with lack of exposure data in road accident analysis

Modelling drivers´ behaviour on tapered on-ramps

Antonio D’Andrea, University of Rome “La sapinza”,Italy

Driver behaviour models and monitoring of risk: Damasio and the role of emotions

Detection and low-cost engineering improvement of inconsistent horizontal curves in rural roads

João Lourenço Cardoso, Laboratório Nacional de Engenharia Civil (LNEC-DVC-NTSR), Portugal

Session 10. DATA AND MODELS

A generic approach for in depth statistical investigation of accident characteristics and causes

Khaled A. Abbas, Egyptian National Institute of Transport, Egypt

A general linear model framework for traffic conflicts at uncontrolled intersections in greater Cairo

Azza M. Saied, Cairo University, Egypt

On the spot accident research in the UK: A new approach to in-depth investigations

Calibrating the run-of the road accident models by full-scale impact tests

Traffic safety on urban streets – The problem and how to assess it

Use of statistical diagnostics and pattern recognition methodologies in developing safety improvement strategies

B. Allery, Colorado Department of Transportation, USA

Session 11. COST AND ENVIRONMENT

Risk factor profile and the cost of traffic injury in a tertiary hospital in Kenya

Economic effectiveness of road safety measures: problems of evaluation

Sweden´s vision zero – the least mourned traffic casualty

Methods for estimating road accident costs – A comparision of costs for a fatal casualty in different countries

Anna Trawén, University of Lund, Sweden

Designing a safe residential environment for children

Sustainable transport policies in metropolitan cities: The way forward

Session 12. SPEED AND SPEED MANAGEMENT

Danish experiences with speed zones/variable speed limits

Intelligent speed adaptation – effects on driving behaviour

The effect of weather controlled speed limits on driver behaviour on a two-lane road

Driving speed relative to the speed limit and relative to the perception of safe, enjoyable and economical speed

David Shinar, Ben Gurion University, Israel

Field test on equipments and devices for the management of vehicular speed and transversal position

Antonio D’Andrea, Giuseppe Cantisani, Department of Hydraulic, Transportation and Roads, University of Rome “La Sapienza”, Italy

Effect of headlights luminance and width between headlight on night driving distance estimation

Candida Castro, University of Granada, Spain

Session 1. ROAD SAFETY ON DIFFERENT CONTINENTS

National road safety strategy in Ghana Per Mathiasen, Carl Bro a/s, Denmark

Relationship between accidents and geometric characteristics for four lanes median separated roads

Ciro Caliendo, University of Naples, Italy

The main problems of road safety in St. Petersburg and ways of their solution Andrey Gorev, Automobile and Road Institute, Russia

Safer guardrail to bridge rail transitions

Charles F McDevitt, Federal Highway Administration, USA

1

NATIONAL ROAD SAFETY STRATEGY, GHANA

Per Mathiasen Carl Bro a/s Tel. +45 43486639 Introduction

In 1998, more than 1,600 people were killed and 11,000 injured in road accidents in Ghana.

But not all accidents and injuries are registered and the actual numbers could be more. The total costs due to accidents are estimated to be at least USD 300 million every year - and increasing.

0 500 1000 1500 2000

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Road accidents occur as a result of several contributory accident factors and effective road safety plans involves joint efforts by many different stakeholders. The Government of Ghana acting through the Ministry of Transport and Communications has therefore established a National Road Safety Commission (NRSC) to develop, promote and coordinate the National Road Safety Strategy. The National Road Safety Strategy will be the main thread for NRSC’s performance in the 5-year period 2001-2005. The purpose of the strategy is to break the upward trend in road accidents and create a basis for concrete, sustainable accident reduction towards 2010. The overall target is a 5% reduction in road fatalities from 1998 as the base year to 2005 and a further 15% reduction before the end of 2010; thereby Ghana can achieve the overall African road safety target of 20% reduction by 2010. The targets correspond to a decrease from 1,600 fatalities in 1998 to 1,520 in 2005. The target for 2010 is 1,280 fatalities.

0 500 1000 1500 2000

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Figure 2. Road Safety Objectives for 2005 and 2010 in Ghana

- 5% - 20%

Figure 1. Development in Road Fatalities in Ghana 1998-2000 Fatalities/Year

Fatalities/Year

Source: BRRI Source: BRRI

2 Stakeholders

The NRSC has identified seven major public road safety stakeholders who will be the mainstays for the implementation of the strategy. These are:

• The National Road Safety Commission and its Secretariat (NRSC);

• The Building and Road Research Institute (BRRI);

• The Driver and Vehicle Licensing Authority (DVLA);

• The Ghana Police Service Motor Transport and Traffic Unit (MTTU);

• The Ghana Highways Authority (GHA);

• The Department of Urban Roads (DUR);

• The Department of Feeder Roads (DFR).

The stakeholders’ weaknesses and strengths have been analysed. Some of the weaknesses are lack of specific budgets and guaranteed funding for road safety activities, and that most staffs assigned to road safety activities are not dedicated to road safety and spend much time on other tasks. Existing accident data are too old, the police have insufficient accident reporting routines, and there is no uniform command in the traffic police, which makes coordinated enforcement difficult. Also, despite that up to 80% of the victims who are declared dead on arrival at hospital die on the way to hospital, Ghana lacks a national emergency service to ensure first-aid and transport to hospitals for all accident victims. Finally, the rapidly increasing traffic is a threat for the set road safety targets. It will be an integrated and challenging part of the strategy to overcome these weaknesses.

Fortunately, the stakeholders are strong on other areas:

• The National Road Safety Commission (NRSC) has a work programme for the next 5 years and the NRSC Secretariat is preparing for its role as coordinator and facilitator and for national campaigns and education;

• Ghana Road Fund, which is responsible for vehicle tax funding of road maintenance, has initiated allocation of funds to road safety;

• The Global Road Safety Partnership has chosen Ghana as one of its focus countries and has established a local organisation in Ghana. It will be the overall coordinating entity for NGO’s working with road safety in Ghana and a strong partner for the NRSC;

• The major road departments are establishing road safety units and have obtained initial donor support for the development of road safety procedures;

• Accident reporting procedures exists within the police and a road safety research unit at BRRI is able to compile and analyse the data;

• New driver education and licensing procedures are well under way with donor support and the Driver and Vehicle Licensing Authority is being strengthened to implement and maintain the new procedures;

• Shell and Mobil have introduced a driver training and testing facility, which has brought the accident toll for its drivers down from 19 fatalities annually to zero. Other companies with heavy vehicle fleets on the road will now be encouraged to follow their example.

Finally, past road safety projects have shown that Ghanaian institutions are able to work

dedicated with road safety. Some of staffs trained earlier are still active and available for

coming road safety activities. Moreover, some of the training materials and manuals

developed earlier can be used again.

3 The NRSC has also identified other stakeholders from the public and the private sectors who can contribute to better road safety. Among these are the Transport Coordinating Council and the oil marketing companies. Private companies have in the past supported funding of road safety campaigns and education of school children. Shell and Mobil have successfully demonstrated that road safety training of drivers can contribute to reduced accident costs for the companies. The NRSC will therefore further strengthen the cooperation with the private sector and support their initiatives fully.

Focus Areas

Based on an analysis of accident data from 1996, which is the latest year from which data is available for the entire country, six major road safety problems have been selected as focus areas for the strategy:

• Accident black spots in urban areas and villages;

• Pedestrians;

• Children;

• Professional drivers;

• Speeding;

• Drunken driving.

The reason for selecting the above focus areas will be stated in the following.

Urban Areas

85% of the accidents in Ghana are concentrated around the Capitol Accra. These most

accident-prone areas comprise the five regions Ashanti, Central, Eastern, Western and Greater Accra.

Moreover, 77% of the fatalities in 1996 occurred in urban areas, including highways passing through villages.

Accidents are concentrated around Accra

Data: 1996 Source: BRRI

Figure 3. Accidents cluster in urban areas around the Capitol

4 The accidents are concentrated on the arterial roads leading to Accra, where the highways pass through village settlements and cities. The coastal road and the Accra-Kumasi road are especially problematic. These roads and built-up areas will get special attention in the coming years.

Road user groups

Minibus (or “Tro-Tro”) occupants account for the majority of the injuries, whereas pedestrians represent the vast majority of the fatalities. Together, minibus passengers and pedestrians constitute the most frequent accident victim groups, representing 62% of all injuries and fatalities. The remainder is distributed among drivers and occupants of cars and trucks and motorcycle riders.

0 500 1000 1500 2000 2500 3000 3500 4000

Tro-tro/bus Pedestrians Car Truck Bicyclists Motorcyclists Others

The picture changes dramatically if we look at fatalities alone.

Figure 5. Injuries and road user groups Urban

77%

Figure 4. Fatalities on urban and rural roads

Data: 1996 Source: BRRI

Data: 1996 Source: BRRI

Rural 23%

Injuries 1996

5

0 50 100 150 200 250 300 350 400 450 500

Tro-tro/bus Pedestrians Car Truck Bicyclists Motorcyclists Others

Fatalities with pedestrians account for almost half of the fatalities. Minibus passengers are the second biggest group, followed by car and truck occupants. Again, bicyclists and motorcycle riders represent smaller numbers because they are less common means of transport, but they are vulnerable and exposed road users with a very high accident risk.

It is obvious that pedestrians are more vulnerable in case of an accident and suffer more severe injuries than other road user groups. Measures that can improve the safety for pedestrians will therefore have a high priority in the years to come. Secondly, minibus drivers and other professional drivers will be an important target group for education and campaign activities. They drive heavy and potentially dangerous vehicles and have a responsibility for passengers and goods every day, and the accident statistics indicate that there is an urgent need to train this driver group.

Age

The distribution of injuries with respect to age groups reflects the age groups that are most active and mobile, the late teenage years to the mid-forties. These people are in the prime of their life, breadwinners, whose sudden absence or disability due to accidents has serious consequences for an entire family.

0 500 1000 1500 2000 2500 3000 3500

0-15 16-30 31-45 46-60 More than 60 Unknown

Figure 6. Fatalities and road user groups

Figure 7. Injuries and age

Data: 1996 Source: BRRI Data: 1996 Source: BRRI

Fatalities 1996

Injuries 1996

6 Children, although they represent a relatively small road user group, have an alarmingly high fatality rate.

0 5 10 15 20 25 30

0-15 16-30 31-45 46-60 More than 60

Children most often transport themselves by walking. But their senses and capabilities are not fully developed and they have difficulties assessing speeds and perceiving dangerous situations. Moreover, their physique makes them extremely vulnerable in case of a collision with a vehicle, whereas adult pedestrians have a greater chance of survival due to their height and stronger physique. Education of children and safer roads to school are therefore important focus areas in the strategy.

Over-speeding

With regard to speed, lack of knowledge about and disrespect for speed limits is a widespread phenomenon in Ghana. Also, proper signing and speed reducing measures are rare. Speeding is a problem both on highways and in urban areas and is considered a major contributory accident factor in Ghana. It is a fact that the breaking length increases with the square of the speed. Speeding therefore gives the driver less time to react in a critical situation and the impact is much more serious when things goes wrong. The connection between speed and accidents is well documented worldwide and there is great potential for accident savings here.

Drunken Driving

Alcohol blunts the senses and reduces the reaction time considerably, hereby increasing the risk of accident dramatically. A study from 1998 (Mock, Asiamah, Amagashie) revealed that drunken driving might be a major contributory accident factor in Ghana.

Of 722 randomly-tested weekend drivers:

• 11% were intoxicated;

• 3% of the bus drivers were intoxicated;

• 8% of the truck drivers were intoxicated;

• 54% of all drunk drivers were coming from a funeral; 40% were habitual drinkers;

• Drunk driving was more common among illiterate, middle-aged drivers.

Drunken driving, or intoxication, is here defined as Blood Alcohol Concentration (BAC) > 80 mg/dl. As a comparison, the percentage of drunken drivers in Denmark and France is 0.4%

and 3.4% respectively.

Data: 1991-1996 Source: BRRI

% of total fatalities 1991-96

Figure 8. Fatalities and age

7 There is little doubt that this is a contributory accident factor in Ghana. The findings from the earlier study points at target groups for campaigns, education, and enforcement activities in the years to come.

Driving without proper training and drivers license

Many minibus and truck drivers struggle every day to make a living. They work hour on hour and pay little consideration to their need for sleep, proper meals, water and their health in general. This leads to exhaustion and fatigue, which reduces the driver’s capabilities

considerably. The drivers are not allowed to work more than 8 hours running, but they often work for 12. Moreover, some drivers practically buy their license without further training or testing, or simply start driving a minibus without even attempting to get a license. Their lack of training and understanding of rules and risks pose a danger to their passengers, their goods, and to other road users every day. As a result, overloading and over-speeding is a common phenomenon among professional drivers. Moreover, a study performed by an ophthalmologist at Korle Bu Eye Clinic revealed that out of 798 screened drivers, 184 needed to wear glasses in order to drive, 45 had cataracts, and 65 had glaucoma and therefore should not be allowed to drive. This means that 37% of the drivers that were screened had impaired vision.

Road conditions

The improvement of roads and highways is an indispensable part of the National Road Safety Strategy. Road improvements can improve road safety locally quickly and effectively when the right measures are used. Presently, the problems that have to be addressed are:

• Inappropriate speed limits;

• Inappropriate road characteristics through build-up areas;

• Poor alignment standards and visual guidance;

• Poor maintenance of pavements;

• Steep shoulders and ditches;

• Hard objects in the roadside;

• Uncontrolled access roads;

• Narrow carriageways.

The strategy will first of all deal with the most serious accident black spots and demands for traffic calming in build-up areas. Secondly, accident-prone routes will be treated section wise.

Objectives and Outputs

The Logical Framework Approach (LFA) was used to describe the strategy’s objectives, outputs (concrete results), activities and resources. The LFA-methodology also implies the definition of key performance indicators to measure and evaluate the progress of the activities.

Consequently, each of the seven major stakeholders have identified:

• Their long term objectives for road safety;

• Their objectives for year 2005;

• The outputs they need to produce in order to obtain the objectives up to the year 2005;

• The activities they need to perform to achieve the outputs;

• The resources they require for producing the outputs.

The NRSC Secretariat will measure the overall progress of the strategy and facilitate the

provision of the needed resources and institutional support.

8 The countermeasures to improve safety within the six focus areas are first of all education, enforcement, and engineering measures.

FOCUS AREA Education Enforcement Engineering

Black spots -

Police enforcement on accident-prone highways

Improvement of accident-prone spots (black spots)

Pedestrians

Awareness campaigns in

the media -

Better road side facilities for pedestrians, safer crossing points

Children

Nationwide road safety education for school children aged 8-9, 12-13

-

Traffic calming on roads nearby schools, safer crossing points

Professional drivers

Formalised driver training programmes, company action plans

Vehicle condition and overloading control -

Speeding

Campaigns against speeding in the media

Systematic enforcement with speed radars on accident-prone highways

Speed reducing measures on highways through villages

Drunken driving

Campaigns against drunken driving in the media

Systematic enforcement with breathalysers on accident-prone highways

-

Responsible MAIN (contributory)

NRSC (DVLA) MTTU (DVLA, GHA) GHA, DUR, DFR

Moreover, to increase the chance of survival and recovery for accidents victims, emergency services has been included in the shape of first aid training and development of a public emergency service. The NRSC has subsequently defined three levels of implementation in order to ensure that the most important outputs are produced first:

• Level 1 – USD 6 million - the most urgent and feasible level, which must be fulfilled before the end of 2005. It ensures funding for education and campaigns combined with police enforcement. Level 1 also comprises institutional building in the stakeholders’

organisations, and pilot schemes for road and emergency service improvements;

• Level 2 – USD 8 million - comprises implementation of road improvements and vehicle inspection measures in a larger scale. Moreover, level 2 further strengthens road safety in institutions that are already in progress with road safety activities.

• Level 3 – USD 14 million - comprises mainly large-scale implementation of black spot improvements, route action plans, traffic calming projects, and major investments in equipment. Level 3 is very ambitious and requires political will and thoroughgoing changes in the road authorities prioritisation of budgets for maintenance and construction. An increase in taxes on fuel and imported vehicles for Ghana Road Fund may also be considered to provide the necessary funds.

Appendix 1 summarises the objectives and outputs for the major stakeholders.

From Strategy to Action

The total cost of the strategy is USD 28 million, covering the implementation of all 3 levels.

This is a very ambitious budget but necessary if the target must be fulfilled. It is most likely

9 that funding will be obtained stepwise in the years to come, and from different sources. It is the hope that the strategy will make it easier for national and international sources to get an overview of potential road safety projects and to choose appropriate projects that are in line with the objectives of the National Road Safety Commission.

The potential savings if the target is fulfilled will be USD 18 million per year in 2005, mounting up to more than USD 70 million per year in 2010. The accumulated savings, due to reduced accident costs for the Ghanaian society, will then be USD 45 million in the period 2001-2005 and minimum USD 260 million in the entire period 2001-2010. The strategy is therefore a very cost-effective investment.

A new national road safety strategy for 2006-2010 will be prepared by the NRSC in 2005 to ensure that the efforts are sustained and – if necessary - increased towards 2010.

NATIONAL ROAD SAFETY STRATEGY

Development objectives

• Safe and secure road transport for general economic development and increased welfare of the Ghanaian society.

Long-term and Year 2005-objectives

• 20% reduction in road fatalities from 1998 to 2010

• 5% reduction in road fatalities from 1998 to 2005

Outputs by 2005

• A strong National Road Safety Commission and Secretariat > Increasing the funding for road safety initiatives;

> Focusing road safety efforts on the most important road safety challenges;

> Promoting road safety awareness in the private sector;

> Coordinating and monitoring road safety initiatives;

> Evaluating the efforts and improving them continuously

• Nationwide road safety education of school children

• Increased awareness among new drivers, professional drivers and general public

• Better accident data

• Dedicated and systematic police enforcement

• Road safety units in stakeholder organisations

• Safer roads

Resources needed

• USD 28 million

• Sufficient and dedicated personnel among stakeholders

RELATIONSHIPS BETWEEN ACCIDENTS AND GEOMETRIC CHARACTERISTICS FOR FOUR LANES MEDIAN SEPARATED

ROADS

C. Caliendo (*), R. Lamberti (*)

(*) Department of Civil Engineering, University of Salerno (**) Department of Transportation Engineering, University of Naples

The effects of geometric characteristics on the accidents of the A3 Naples-Salerno, which is among the riskiest motorway in Campania (Italy), are reported in this paper. For the purpose, all the accidents which occurred during a twenty month period (August 1998 - March 2000) from Km 5+00 to Km 55+00 (for a section of 50.0 km) have been examined. All the information on the accidents were taken from the Road Police reports, while the horizontal and vertical alignments were obtained from the road plan.

The study was carried out by the univariate analysis therefore the accident data were related to the following single variables: length of tangents, radii of circular curves( R ), longitudinal grade(± ^i), change in operating speeds between two consecutive geometric elements having constant curvature (∆V) and sight distance. Therefore relationships between these geometric parameters and the accidents which occurred on the motorway studied, that is a four-lanes median-separated road, have been developed.

The accident data have also been related to the pavement surface conditions, so relationships to the Side Friction Coefficient (CAT) and macro-texture (HS) have been developed too.

1. Introduction

Since road safety is a primary consideration in relation to the high social cost of accidents, in Italy road accidents cause 6500 deaths and 260000 injuries per year with a cost of 12500 million of ECU [1], the studies having the aim of determining the effects of different components on accidents remain a matter of continuing interest.

Road safety depends mainly on the relationships among three components: human factors (perception of information of the road characteristics, driving behaviour and psychophysical capabilities); vehicle (performance and tyre-road interaction); environment (horizontal and vertical alignment, sight distance, pavement conditions, safety barriers, signals and lighting).

Connected to the objectives aimed at improving road safety, there are numerous research studying the parameters above mentioned; in order to individuate some of their combinations to which a higher responsibility on the accidents can be attributed [2-8]. A lot of accident data are required to achieve this purpose; furthermore there is a need to first of all understand the dynamic of the accidents and then to weigh the causes, to formulate hypothesis on the relations among the parameters that are involved and to estimate the consequences. Estimation of the combined effects on the safety of the simultaneous three component (driver, vehicle, environment) is therefore rather difficult. However among these, the road represents one of the most important factors.

The aim of this paper is to provide a contribution in the evaluation of the effects of main geometric characteristics and pavement conditions on accidents for four-lane median-separated roads.

For the purpose all the accidents which occurred during a twenty month period (from August 1998 to March 2000) on the A3 Naples–Salerno, which is among the riskiest motorway in Campania

(Italy), from Km 5+00 to km55+00 (for a road section of 50 Km) have been examined. To achieve the aim all the information both on the accidents and on the weather, taken from the Road Police reports, have been collected. The horizontal and vertical alignments of the studied road section were obtained from the road plan.

The accident data were connected to the main geometric variables such as: length of tangents, radii of circular curves, longitudinal grade, sight distance, change in operating speeds between two consecutive elements having constant curvature.

The accident data were furthermore related to the surface pavement conditions specified by means of CAT (Side Friction Coefficient) and HS ( macro-texture).

The analysis has been carried out regarding the variables separated, and showing that as their values change the accidents increase or decrease.

The results provide interesting engineering judgements aimed at reducing the number of accidents on the four lanes median-separated roads.

2. Methodology of Study

To achieve the aim indicated in the introduction all the accidents which occurred during a twenty month period on the Naples-Salerno motorway were examined. The total number of accidents surveyed in this period were 800; of which, after a detailed analysis of the Road Police reports, only 572 accidents can be attributed to the road geometric characteristics far away from the intersections.

The accident data, as already mentioned, were related to horizontal and vertical alignments (length of tangents, radii of circular curves ( R ) and longitudinal grade (± i). Because the road safety on a circular curve is influenced not only by the curve's radius, but also by both the geometry of adjacent segments and by the length of road ahead visible to the driver, the accidents were related to change in operating speeds between two consecutive geometric elements (∆V) and to sight distance too.

In addition to geometric characteristics pavement surface conditions also have safety implications, therefore accidents were associated with Side Fiction Coefficient (CAT) and macro-texture (HS) too.

In the analysis every geometric element category has been grouped in classes which have an appropriate range. The accidents which occurred on the geometric elements, belonging to each class, have been summed and then divided by the number of the elements themselves contained in the class, yielding so an average number of accidents. This average number of accidents has then been related to the central point of each class.

The results obtained are contained in figures that with their co-ordinates individuate the average number of accidents (vertical axis) and the central point of each class (horizontal axis). The relative curves give a graphical representation of the regression and R² is its coefficient of correlation.

3. Horizontal-Vertical Alignments of the Naples-Salerno Motorway

The A3 motorway that links up the two towns of Naples and Salerno is a type III according to the standards of the Italian Research Council (CNR/80) [9], with a design speed range V = 80÷100Km/h.

The cross section is a four–lanes median-separated road with the width of each lane of 3.5m, shoulders of 1.5 m and median of 1.10m (18.60m for total cross section). A longitudinal steel barrier in the centre of median is also contained.

In the horizontal alignment there are tangents (lengths from 62 m to 4503 m) and circular curves (radii from 208 to 2573 m) without transition curves. In the vertical alignment there are gradients from 0 to 5.2% and circular vertical curves.

The geometric characteristics and the number of accidents which occurred during the above mentioned period on each element having a constant curvature (tangent or circular curve) both on the North carriageway (direction Naples) and on the South carriageway (direction Salerno) are contained in table 1. In the last column of this table is also the total number of accidents which occurred on the two directions.

Tab.1- Horizontal Geometric Characteristics of the Naples-Salerno Motorway (from Km 5+00 to km 55+00) and Accidents which Occurred (from August 1998 to March 2000)

From km To km R(m) L (m) Acc.

NA-SA Acc.

SA-NA Tot.

Acc.

5 5,984 T ∞ 984 6 13 19

5,984 6,769 C 2040 785 5 12 17

6,769 8,5 T ∞ 1731 12 24 36

8,5 9,125 C 2573 625 6 12 18

9,125 9,454 T ∞ 329 0 2 2

9,454 9,899 C 2495 445 0 4 4

9,899 11,876 T ∞ 1977 26 22 48

11,876 12,331 C 1161 455 1 1 2

12,331 13 T ∞ 669 2 1 3

13 13,329 C 1111 329 2 1 3

13,329 13,707 T ∞ 378 2 1 3

13,707 13,968 C 475 261 3 3 6

13,968 18,471 T ∞ 4503 34 27 61

18,471 18,722 C 660 251 1 3 4

18,722 19,099 T ∞ 377 4 0 4

19,099 19,402 C 632 303 3 0 3

19,402 21,924 T ∞ 2522 25 13 38

21,924 22,206 C 398 282 6 13 19

22,206 22,434 T ∞ 228 0 2 2

22,434 22,954 C 452 520 9 2 11

22,954 24,581 T ∞ 1627 4 10 14

24,581 24,88 C 898 299 0 1 1

24,88 25,66 T ∞ 780 3 13 16

25,66 25,981 C 350 321 0 1 1

25,981 26,717 T ∞ 736 2 5 7

26,717 26,96 C 1000 243 0 1 1

26,96 29,117 T ∞ 2157 6 6 12

29,117 29,26 C 800 143 0 2 2

29,26 29,8 T ∞ 540 4 2 6

29,8 30,125 C 1666 325 0 7 7

30,125 30,4 T ∞ 275 0 1 1

30,4 31,4 C 1000 1000 0 1 1

31,4 31,85 T ∞ 450 0 4 4

31,85 32,4 C 1000 550 3 4 7

32,4 34,736 T ∞ 2336 11 7 18

34,736 34,95 C 435 214 2 2 4

34,95 35,077 T ∞ 127 0 0 0

35,077 35,246 C 413 169 0 0 0

35,246 35,9 T ∞ 654 2 3 5

35,9 36,35 C 637 450 10 3 13

36,35 37,1 T ∞ 750 7 7 14

37,1 37,455 C 493 355 0 0 0

37,455 39,145 T ∞ 1690 4 1 5

39,145 39,493 C 830 348 3 1 4

39,493 40,597 T ∞ 1104 7 8 15

40,597 40,964 C 950 367 0 1 1

40,964 41,488 T ∞ 524 0 10 10

41,488 41,89 C 835 402 0 1 1

41,89 42,014 T ∞ 124 0 2 2

42,014 42,213 C 460 199 0 0 0

T = tangent C = circular curve

L(m) = length of geometric element R(m) = radius of curve

Acc. NA-SA = accidents which occurred on the South carriageway (direction Naples)

Acc. SA-NA = accidents which occurred on the North carriageway (direction Salerno)

Acc. Tot. = total accidents which occurred on the two directions

From km to km R(m) L(m) Acc.

NA-SA Acc.

SA-NA Tot.

Acc.

42,213 42,804 T ∞ 591 1 2 3

42,804 43,082 C 630 278 4 6 10

43,082 43,214 T ∞ 132 0 0 0

43,214 43,672 C 587 458 1 0 1

43,672 44,721 T ∞ 1049 1 2 3

44,721 44,82 C 319 99 0 1 1

44,82 44,981 C ∞ 161 0 0 0

44,981 45,225 C 1387 244 0 1 1

45,225 45,495 T ∞ 270 1 2 3

45,495 45,614 C 300 119 3 2 5

45,614 45,712 T ∞ 98 1 1 2

45,712 45,925 C 211 213 1 0 1

45,925 46,179 T ∞ 254 1 1 2

46,179 46,307 C 380 128 0 0 0

46,307 46,845 C 460 538 0 5 5

46,845 46,975 T ∞ 130 0 0 0

46,975 47,089 C 208 114 1 0 1

47,089 47,286 C 397 197 1 1 2

47,286 47,486 T ∞ 200 2 10 12

47,486 47,7 C 295 214 1 7 8

47,7 47,954 C 240 254 1 2 3

47,954 48,09 T ∞ 136 1 0 1

48,09 48,3 C 322 210 1 3 4

48,3 48,518 T ∞ 218 1 2 3

48,518 48,7 C 265 182 0 0 0

48,7 49,317 C 220 617 2 2 4

49,317 49,379 T ∞ 62 0 0 0

49,379 49,625 C 218 246 2 4 6

49,625 49,769 T ∞ 144 0 0 0

49,769 49,904 C 327 135 1 0 1

49,904 50 T ∞ 96 0 0 0

50 50,142 C 283 142 0 0 0

50,142 50,56 T ∞ 418 2 1 3

50,56 50,665 C 750 105 0 0 0

50,665 50,775 C 510 110 0 0 0

50,775 50,956 T ∞ 181 0 0 0

50,956 51,138 C 500 182 2 1 3

51,138 51,713 T ∞ 575 7 2 9

51,713 51,925 C 475 212 0 0 0

51,925 52 T ∞ 75 0 0 0

52 52,245 C 304 245 0 0 0

52,245 52,466 T ∞ 221 0 0 0

52,466 53,182 C 415 716 0 0 0

53,182 53,278 T ∞ 96 0 0 0

53,278 53,609 C 302 331 0 0 0

53,609 53,85 T ∞ 241 0 0 0

53,85 54,033 C 446 183 0 0 0

54,033 54,17 T ∞ 137 0 0 0

54,17 54,334 C 337 164 0 0 0

54,334 54,787 T ∞ 453 0 0 0

54,787 55 C 530 213 0 0 0

Total 50000 254 318 572

3. Accident Rates

Table 2 contains the accident rates (accidents/10⁸ vehicle kilometre) for a single carriageway and for the whole motorway, the accident rates in relation to tangents and curves are then reported.

The average daily traffic (TGM) used in analysis was obtained from in situ traffic surveys. During the period studied (from August 1998 to March 2000, then per 609 days) the TGM values were considered constant and equal to 73.343 vehicles/day.

Tab.2 - Accident Rates (accidents/10⁸ vehicle kilometre) Geometric

elements

Accidents Traffic for carriageway

Length (km) Acc./10⁸ Vehicle.km North carriageway (SA-NA) Tangents+curves 318 (73.343 / 2)*609 50 28.4

South carriageway Sud (NA-SA) Tangents+curves 254 " 50 22.7

Both the carriageways Tangents+curves 572 " 2*50 25.6

North carriageway (SA-NA) Tangents 207 " 33.51 27.6

Curves 111 " 16.49 30.1

South carriageway d (NA-SA) Tangents 179 " 33.51 23.9

Curves 75 " 16.49 20.3

Both the carriageways Tangents 207+179=386 " 2* 33.51 25.7

Both the carriageways Curves 111+75=186 " 2*16.49 25.2

This table shows that the accident rate on the North carriageway is higher than on the South one (28.4 accidents/10⁸ vehicle kilometre instead of 22.7 accidents/10⁸ vehicle kilometre), having an increase of 25%. The average accident rate on the two directions is of 25.6 accidents/10⁸ vehicle kilometre.

On the North carriageways, the accident rates of the tangents is higher than that of the curves (30 accidents/10⁸ vehicle kilometre against 27.6 accidents/10⁸ vehicle kilometre), the opposite happens on the South carriageway. In relation to the two directions there is no difference between the accident rate of the tangents and the circular curves.

As can be seen the accident rate of the road studied (25.6 accidents/10⁸ vehicle kilometre) is lower than those generally contained in current international literature. This is due to the fact that in Italy only the accidents which cause heavy consequences are surveyed and recorded by the Road Police.

This is generally done, by an ordinary network, only when there are fatalities, injuries and/or the vehicle is very much damaged. Therefore the number of accidents used in the analysis is only a small part of the accidents which in reality occurred. The accidents which have not been surveyed remain only in the mind of the drivers that unluckily collided and/or in the archives of insurance agencies.

4. Relationships between Accidents and Geometric Characteristics 4.1 Accidents-Length of Tangents

The total number of accidents that can be attributed to tangents is 386 of which 207 accidents occurred on the North carriageway and 179 on the South carriageway.

For each carriageway, the analysis was carried out following the approach above mentioned:

tangents have been considered in growing order according to their length and they have been grouped in classes which have ranges of 50 m. The accidents surveyed for each tangent, belonging to each class, have been summed and then divided by the number of tangents contained in that class, yielding so an average number of accidents for each class. To this value then an average length of tangents has been associated, which was individuated in the central point of each class.

Figures 1 and 2 individuate, with their co-ordinates, the average values above mentioned both for the North carriageway and for the South carriageway. Each curve gives a graphical representation of

the regression and R² is its coefficient of correlation. Figure 3 makes reference, instead, to the accidents which occurred on both carriageways.

y = 8E-07x² + 0,0042x R² = 0,7655

0 5 10 15 20 25 30 35 40

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Fig.1- Average Number of Accidents-Length of Tangent (North carriageway )

y = 0,0056x + 0,9214 R² = 0,5448

0 5 10 15 20 25 30

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Fig.2- Average Number of Accidents-Length of Tangents (South carriageway )

y = 3E-07x² + 0,0055x R² = 0,6524

0 5 10 15 20 25 30 35 40

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Fig.3- Average Number of Accidents-Length of Tangents (both carriageways)

The trends obtained show that the average number of accidents increases with the length of tangents. This happens because of the higher vehicle speeds on the longer tangents and because of the overcoming of the friction available in the contact area between tyre and road pavement.

There is a broad agreement between these three trends, but the dispersion of accident data (indicated with the low values of the correlation coefficients R²) points out that the length of tangents can seldom be considered as the only hazardous factor.

Note that the average number of accidents for example relative to a length of tangents of 1000 m is about 2.0 times that of 500 m.

4.2 Accidents- Radius of Curvature

The curved sections have been analysed by means of this approach: radii of curvature have been grouped, for each carriageway, in growing classes which have ranges of 50 m. The accidents surveyed for each circular curve, belonging to each class, have been summed and then divided by the number of curves that were in that class, having so an average number of accidents. To this value an average radius of curve has been associated, individuated in the central point of each class.

In figure 4 are contained, for example, only the results obtained for the whole motorway because similar trends were found for each direction too.

It shows, even if in a qualitative manner because of the sparse data do not allow a statistical approach, that the average number of accidents decreases as the radius of curve increases. This confirms the general opinion that the accidents are much more frequent on curves having smaller radii because of increased centrifugal force placed on the vehicle.

Fig. 4. Average Number of Accidents-Radius of Curvature

The average number of accidents has been found as function of radius only per R≤ 500m. Note that the average number of accidents relative to a radius of 200 m is about 2.0 times that of a radius of 400 m. A similar trend has also been obtained when the authors have related the radii of curves to the accident rates (accident /10⁸ vehicle kilometre), taking also thus account of the traffic and the lengths of the curves.

Because of the small size of samples, the authors propose that further studies be conducted so as to have a large data base in this field for the four-lanes median-separated roads.

However there is a reasonable agreement with the international literature even if it concerns the accidents on the two-lanes road: for radii of grater than about 400 to 500 m an increase in radius lead to a low-level safety gain; with radii of 200 have accident rates that are about twice those on sections with radii of 400m.

Note that the minimum horizontal curve radius according to Italian standards (R =250 m with a design speed V =80 Km/h) [9] presents a lot of accidents. Therefore geometric design standards that are mainly based on logically derived relationships and engineering judgements are not always validated by accident studies.

4.3 Accidents-Longitudinal Grade

In analysis, we have separated the accidents which occurred on upgrades from those on downgrades. Accidents have then been put in order in relation to the increase of the absolute value of grade |i%|. We have constituted classes of grade having ranges of 0.5%. Accidents, belonging to each class of grade, have been summed and then divided by the total number of horizontal geometric elements (tangents and circular curves) that were in that class, having so an average number of accidents. To this an average grade has then been associated, individuated in the central point of each class of grade. Analysis has been carried out both for each carriageway and for the whole motorway.

Figure 5a shows in relation to the two directions that the average number of accidents depends on the downgrades when | i | > 2.5%. Similar trends were also found for each carriageway.

0 0,5 1 1,5 2 2,5 3 3,5

0 250 500 750 1000 1250 1500