Safety Performance Indicators for the Road Network
W Weijermars, SWOV, NL; V Gitelman, Technion, IL; E Papadimitriou, NTUA, GR; C Lima de Azevedo, LNEC, PT
This paper discusses two SPIs that were developed for Roads within the 6th FP European project SafetyNet. Together the SPIs assess the level of safety of the road network (outside cities).
Road safety can be assessed in terms of the social costs of crashes and injuries. However, the numbers of crashes and people killed or injured are small and do not provide all the necessary information about the level of road safety. Indicators like seat belt usage rates, speeds, and alcohol usage rates provide information about underlying causes of crashes. These indicators can assist in assessing the current safety conditions of a road traffic system and in monitoring their progress. Furthermore, they can be used to compare the safety performance of countries or regions and to measure the impact of various safety interventions. Within the 6th FP European project SafetyNet, a team has worked on the development of Safety Performance Indicators (SPIs) on seven road safety related areas. These SPIs reflect the operational conditions of the road traffic system that influence the system?s safety performance. SPIs were developed for the following areas: alcohol and drug-use, speeds, protection systems, daytime running lights, vehicles (passive safety), roads, and trauma management. This paper discusses the Safety Performance Indicators that are developed for the area Roads.
For Roads, two SPIs were developed that together assess the level of safety of the road network (outside cities). The first one, the 'road network SPI', deals with the functionality of the road network. The second, the 'road design SPI', assesses the safety related to the design of individual roads.
The road network SPI assesses whether the 'right road' is in the 'right place'. First, it is determined which cities should be connected to each other and by what type of road. For that purpose, we propose an internationally harmonized road categorization. This categorization consists of five road categories, ranging from highways to rural access roads. The road category that should be present between cities (the appropriate road category) is dependent of the sizes of the cities that the road connects. The size of a city represents its importance. The appropriate road category is subsequently compared to the actual road category. The SPI is defined as the percentage of appropriate current road category length per road category.
The road design SPI assesses the design of individual roads and is based on the EuroRAP Road Protection Score (RPS). The RPS is a measure for the protection that is provided in relation to three main accident types: run-off road, head-on impacts and severe impacts at intersections. EuroRAP designed a method to calculate the RPS for each road segment or route, expressed in one to four stars. The road design SPI is the distribution over one to four stars per road category.
To evaluate their applicability, these SPIs were applied in a number of pilot countries, i.e. Greece, Israel, Portugal and the Netherlands. The road design SPI is only applied in the Netherlands. For the pilot area, EuroRAP RPS scores were available. It was easy calculate the road design SPI on the basis of the RPS scores. However, it has to be noted that it is not published yet how exactly EuroRAP calculates the RPS scores on the basis of values on various road characteristics. For the transparency and a proper interpretation of the results it is however important that it is published how the RPS scores are calculated.
The road network SPI is applied in all pilot countries. From these pilot projects it was concluded that it is indeed possible to apply the SPIs in practice, although the method for calculating the SPI has some limitations. The importance of the city is for example represented by the number of inhabitants. In some cases, the number of inhabitants was not a good indicator. A solution would be to take other factors like surface of industrial areas and recreational areas into account. However, this would result in a too complicated method. On the basis of the results of the pilots, we developed guidelines for applying the method.
We recommend to apply the road SPIs in order (1) to obtain more insight into the current safety condition of the road network, (2) to be able to monitor developments in the safety condition of the road network, (3) to be able to compare the safety conditions between different regions and countries in an uniform way, and (4) to be able to measure the impact of infrastructure related safety interventions.
Association for European Transport