Road network safety ratings
Road network safety ratings
Road assessment programmes have been developed in recent years to monitor the safety quality of the road network and to draw attention to the need for improvements. Such programmes have predictive ratings which look at the protective quality of various elements of a road network as well as retrospective elements which involve risk-mapping and performance tracking according to specific protocols. A variety of safety ratings are in use or in development:
European Road Assessment Programme
Developed as a sister programme to Euro NCAP, the EuroRAP programme was piloted in 2001 in four countries and has now launched in twenty European countries. EuroRAP currently provides risk ratings and star ratings for major rural roads in several European countries. The work focussed on major roads outside built-up areas, because it is on these roads that most deaths in Europe occur. The aim has been to cover a network of interurban roads on which at least 30% of national fatalities occurred. Route lengths within the EuroRAP networks typically average around 20kms, but many of the links are much shorter. Comparisons are made between roads of similar types, both within and between countries. While the focus is mainly on car occupants, the aim is to extend the programme to include the safety performance of roads for all users in due course.
- To reduce death and serious injury on European roads rapidly through a programme of systematic testing of risk that identifies major safety shortcomings which can be addressed by practical road improvement measures;
- To ensure assessment of risk lies at the heart of strategic decisions on route improvements, crash protection and standards of route management;
- And to forge partnerships between those responsible for a safe roads system - motoring organisations, vehicle manufacturers and road authorities.
Three main predictive and retrospective rating protocols have been developed by EuroRAP for a systematic approach to road assessment: EuroRAP analyses aim to contribute at three levels - providing a systematic audit of the road network, understanding the sources of risk, and indicating the priorities for network improvement .
|EuroRAP's rating protocols|
|Risk mapping||Colour-coded maps showing the risk of death and serious injury that road-users face on different roads with extra mapping for road authorities|
|Performance tracking||Identifying whether fewer people are being killed or seriously injured on a road over time and identifying the countermeasures that are most effective|
|Star Rating||A Star Rating showing how well a road protects road-users if a crash occurs.|
Predictive safety rating protocols
Star Rating: Star Rating is a scale showing how well a road protects the user from death or serious injury once a crash occurs. The aim of the assessment is to evaluate the safety that is 'built in' to the road through design, in combination with the way traffic is managed on it. Data on road design and the standard of a road's safety features is collected by drive-through inspections in specially equipped vehicles. Large scale inspection has taken place in Sweden and Germany. Trained inspectors assess and score each road's safety features and hazards, either in real time (as the road is driven), or later from video images captured along the route. This standard inspection formula can be used on a variety of road types and allows roads across Europe to be assessed and compared on the same basis. EuroRAP's Star Rating differs from normal road safety audits in that the aim is to assess the general standard of a route not identify individual blackspots. The scoring system is based on the road design elements that correspond to each of the four main crash types on Europe's roads.
The elements of EuroRAP's Safety Rating scoring system
- Head-on Crashes: measures of how well traffic lanes are separated
- Run-off Crashes: checks for roadside protection (for example, safety fencing protecting rigid poles, lampposts and trees)
- Junction Crashes: checks for junction layout and frequency
- Pedestrians and Cyclists: checks for facilities and separation from vehicles where vulnerable road-users are present
The protection scoring system is closely linked to vehicle speed, and demonstrates that an appropriate balance between speed and road design can produce high levels of protection on most road types. The initial focus on scoring the passive safety of the road allows a direct link to be made with vehicle safety assessment by considering injury severity in both cases as a function of the biomechanical forces involved in the impact. To make this link, minimum relative risks for the RPS rating are based on the speeds at which car occupants can be expected to survive an impact in a car rated highly in EuroNCAP - 70km/h or below for head on crash protection, 50km/h for intersection crashes and run off crashes (although here occupant protection will depend on the nature of the obstacle hit) and 30 km/h for impacts with pedestrians. Pedestrian and vehicle movements would need to be segregated on any roads with higher speed limits, in order to gain maximum RPS ratings for this crash type.
A review in 2004 of EuroRAP Road Protection Scores showed that:
- On many roads there is substantial scope to improve the potential for injury prevention and crashes involving fatal injury will continue unless this is done.
- On average, single carriageway RPS scores are lower than divided (dual carriageway) roads. Single carriageways show more variability in their design and associated protection from injury.
- Many roads score poorly for run-off protection, reflecting the fact that fatal injuries are likely to occur unless barriers or very wide safety zones can be provided. There is considerable variability in run-off protection along individual routes.
- The lowest scoring roads score poorly for all three crash types - head-ons, single-vehicle runoffs and those at junctions.
- Most of the divided roads that have been assessed do not score the full four stars available, even though they are the safer roads in all highway networks. Scope remains to reduce serious injuries from crashes at uncontrolled junctions and from vehicle run-offs.
- On ordinary 2-lane roads, despite the lower speeds adopted, protection is often limited by narrow safety zones, poor access provision and by the lack of measures to limit the interaction of opposing traffic streams. Some good examples of median treatment of these roads can be seen in Sweden, the Netherlands and Ireland.
Source: (Lynam et al, 2004)
Within the European Union, road inspections have already been extensively used in Sweden and Germany, and trialled in Britain, Ireland and Northern Ireland, the Netherlands and Spain. Results from the four largest of these show that, for example, between a quarter and a half of motorways in these countries fail to score four stars, mainly due to lack of high quality roadside protection . However, the pressing need is to find better median, run-off and junction protection at reasonable cost on single carriageway roads. For EuroRAP results on the protection a road provides in the event of a crash in several European countries, see Star Rating results.
Road Protection Star Rating in Sweden
Sweden was the first to begin and publish a programme of Star Rating based on the EuroRAP RPS protocol. Using a specially equipped Toyota Hiace loaned to the programme from Toyota Sweden, inspections started in October 2003 and covered 1,000km of the national road network, concentrating on two main roads between Stockholm and Gothenburg. Pilot results were launched in February 2004, and proved to be of great interest to the media, professionals and the public alike.
Inspections continued in 2004 with the addition of data for a further 7,090km. Results for 3,780km in the south of the country were launched in December of that year, whilst 3,310km in the north were launched in February 2005.
Of particular significance in the Swedish programme has been the finding that a correlation exists between the number and location of fatal accidents and the Star Rating awarded to particular road sections. Sections with a high number of fatalities generally received a poor Star Rating.
Retrospective safety rating protocols
Risk Mapping is a way of measuring and mapping the number of crashes on individual road sections.
Under EuroRAP's Risk Mapping protocol, safety indicators based on the road network, crash numbers and traffic flow are used to produce four maps:
- Risk per kilometre
- Risk per vehicle kilometre travelled
- Risk in relation to roads with similar flow levels
- Economic potential for crash reduction
Risk is divided into five coloured bands from high-risk (black) to low risk (green). EuroRAP maps give various insights into risk and are designed to support messages aimed at the differing needs and levels of expertise of the target audiences, ranging from the public through to road engineers and policymakers. For example, EuroRAP explains that the maps directed to policymakers and roads authorities comprise:
- Crash density - showing crash rates per kilometre of road, illustrating where highest and lowest numbers of crashes occur within a network.
- Crash rate in relation to similar roads - comparing the crash rate of similar roads with similar traffic flows, illustrating which road sections have a higher rate. Separate road groups are considered - for example, motorways, main roads with traffic flows below 10,000 vehicles per day, main roads with daily traffic flow between 10,000 and 20,000 vehicles per day, and main roads with daily traffic flow greater than 20,000 vehicles per day.
- Potential for crash reduction - providing information on the number of crashes that might be saved if crash rates of road sections, with risk above the average roads of a similar flow, were reduced to the average or to an alternative defined standard risk. This information can be used for considering investment decisions, providing authorities and policy-makers with a valuable tool for estimating the total number of crashes that could potentially be avoided if safety on a road were improved. Used with cost information, this map can indicate locations where the largest return on investment can be expected.
Results to date indicate that there are large differences in fatality rate between groups of countries for similar road types. For example, rates for Spanish motorways are more than four times than those in Sweden, Britain and the Netherlands, and rates in Austria and Belgium more than double. Fatal accident rates for Dutch and Swedish 2-lane roads are the lowest although only roads in the national networks are included in these countries. Higher rates in UK and Ireland reflect in part the greater incidence of small urban areas along these routes. Junction risk is the most important component in Britain while run-off accidents give rise to the highest proportion of risk in Spain . For EuroRAP results on risk mapping in ten European countries, see Risk Mapping results
Risk Mapping in Spain
Spanish Risk Mapping began in 2002 with the production of a pilot risk map for Catalonia - the first time that such information had been made publicly available.
Progressively, the Spanish EuroRAP programme has been extended to cover the complete road network, including over 20,600km of the national system.
In 2003 the first map illustrating risk on the Spanish RCE (Carreteras del Estado) was published. The most dangerous region was found to be Galicia, with 52% of road sections in the area categorised as high (black) or medium-high (red) risk. Examination of results by province showed Pontevedra, Lugo, Asturias and Burgos to have the highest risk overall.
In 2004, further developments were made with the publication of both an accident density map and updated risk map - the first time national EuroRAP results had been launched using both forms of information. The meaning of risk was not well understood by the Spanish public and density maps were used to explain how road administrations set priorities for action and the connection between high traffic flows and high accident numbers. Mapping will be extended to the Navarra and Basque regions.
Performance Tracking is a way of tracking the number of crashes occurring on individual road sections over time - which are getting safer, which are getting worse, and which are staying the same. The EuroRAP process of tracking the performance of road sections over time has several stages: data is initially analysed to identify road sections which have shown a reduction in the number of collisions over time and those where there has been little or no change; data for individual years is then checked to assess consistency of the patterns; and finally, highway authorities are asked for information on remedial, enforcement or education measures that have been implemented that might explain the reduction in crashes. For EuroRAP results of performance tracking in several European countries, see Performance Tracking results
The EuroRAP protocol is currently being extended to include crash likelihood and to consider risks associated with modes other than car.
Other national and international road assessment programmes
Following on from the successful development of EuroRAP, AusRAP and USRAP have now been formed based on the EuroRAP philosophy and basic methodology. Similarly, iRAP has been formed as an international umbrella association to develop road assessment worldwide
Australian Road Assessment Programme (AusRAP)
AusRAP aims to provide a safety rating for the national highway network across Australia. This will generate consumer information for the public and give road engineers and planners vital benchmarking information to show them how well, or badly, their roads are performing compared with others, both in their own and other countries. AusRAP is an initiative of the Australian Automobile Association (AAA). AAA is the national association of Australia's State and Territory motoring clubs and its first report was published in 2005. The objectives are:
- To reduce deaths and injuries on Australia's roads by systematically assessing risk and identifying safety shortcomings that can be addressed with practical road-improvement measures
- To put risk assessment at the heart of strategic decisions on road improvements, crash protection and standards of road management.
AusRAP uses two protocols:
- Risk Mapping, based on a road's history of casualty crashes and traffic flow. Previous AusRAP reports, released in 2004 and 2005, used risk-maps to provide a measure of the safety performance of the AusLink National Network. Road crash fatalities on this network typically account for around 15%of annual road deaths in Australia
- Star Ratings which include the influence of crash likelihood as well as injury severity, involve an inspection of a number of design elements such as lane and shoulder width as well as, for example, the presence of safety barriers. Between 1 and 5-stars are awarded to road links depending on the level of safety which is 'built-in' to the road. The star ratings do not take into account a road's crash history.
US Road Assessment programme (usRAP)
Influenced by success of EuroRAP and AusRAP, usRAP commenced with a pilot study risk mapping of the rural road system in two States in 2004 and published findings in 2006. The second and current pilot phase involves risk mapping in two further states and performance tracking in original mapped states. usRAP is seeking to ensure development in line with international standards.
International Road Assessment Programme (iRAP)
iRAP is an iniatitive supported by the World Bank and the FIA Foundation aimed at developing risk mapping and audit protocols for low to middle income countries. The World Bank has signed a Memorandum of Understanding with the International Road Assessment Programme (iRAP) for a five-year collaboration to develop a business plan for designing and then implementing iRAP's road risk mapping and road audit protocols. The agreement will be overseen for the Bank by the Global Road Safety Facility, hosted at World Bank headquarters in Washington D.C iRAP is currently developing protocols in South Africa, Malaysia, Costa Rica and Chile. An inspection system is being used as a substitute for crash injury data to give an assessment of priorities for remedial treatment. iRAP will look at risk mapping and road protection scores for all road users since in low to middle income countries crashes involving vulnerable road users form a large part of the death toll. It is a particularly interesting development for high income countries too, since it will provide a focus for developing the rating system both to take account of urban environments, and to consider the likelihood and protective factors associated with vulnerable road users.