This document provides details about the theory behind the development of Safety Performance Indicators (SPIs) in seven major areas which are central to the fields of activity in road safety in Europe. The fields of activity were selected as a result of reviews of national road safety plans in many of the EU countries and around the world and are considered the central themes of activity in road safety, necessary to bring about a significant improvement in road safety in the EU countries.
Within each field SPIs were developed which are directly related to that field of activity, can be quantitatively measured, can provide the basis for the assessment of the level of road safety in each country and can serve as an indicator to describe the level of activity in that field and country and can provide a yardstick for comparison. Comparisons can be before and after certain actions are taken or can be comparisons between countries.
As stated above, this document deals with the theory behind the development of each of the seven SPIs. It provides the rationale behind their development, the proofs for their relevance in the specific fields and the existing limitations that led to the adoption of the specific SPIs. The document provides also some recommendations for the possible improvements required to obtain better SPIs. Two companion documents are also being prepared. One is a manual which provides details on the procedures necessary to collects the required data for the development of each SPI in each country. The second document provides results on the data collected so far for each of the 25 EU countries and the SPIs developed so far, based on the data submitted by each of the countries. It can be seen that a lot of work still has to be done, both in collecting the necessary data and in improving the SPIs, once better and more detailed data becomes available.
Alcohol and drugs
Due to the limitations in the current state of accident data collection and data from surveys on the levels of alcohol and drugs in the driving population, three SPIs are proposed:
- The number and percentage of severe and fatal injuries resulting from road accidents involving at least one active road user impaired by psychoactive substance (concentration above a predetermined impairment threshold);
- The percentage of fatalities resulting from accidents involving at least one driver impaired by alcohol;
- The percentage of fatalities resulting form accidents involving at least one driver impaired by drugs other than alcohol.
The first one is not yet possible to realise. Consequently the two latter ones are proposed as
realisable for some countries at present.
Speeds
The speeds that are most relevant for safety purposes are spot speeds measured at various locations on the road network during periods when traffic can be considered free flowing, i.e not during periods of congestion when speeds are severely restricted. The SPIs developed are the mean speed, the standard deviation, the 85th percentile speed and the percentage of drivers exceeding the speed limit. These indicators should be segregated by road type, vehicle type, period of day and period of the week, i.e week-days and weekends. For road types it is suggested to adopt the classification developed in the roads task. In the manual document procedures are developed and described to obtain statistically valid results on a national basis, calculated from the sample of sites at which speeds are measured.
Protective systems
The major protective systems in vehicles that are relevant for the development of SPIs are seat belts for adults and for children, in various types of vehicles and the use of safety helmets by cyclists, moped riders and motorcyclists.
The SPIs developed are:
Set I: Daytime wearing rates of seat belts
SPI A – Front seats – passenger cars + vans /under 3.5 tons/
SPI B – Rear seats – passenger cars + vans /under 3.5 tons/
SPI C – Children under 12 years old - restraint systems use in passenger cars
SPI D – Front seats – HGV + coaches /above 3.5 tons/
Set II: Daytime usage rates of safety helmets
SPI F – Cyclists
SPI G – Moped riders
SPI H – Motorcyclists
All the indicators should come from independent observational surveys carried out on an annual basis, according to sampling procedures described in the Manual and in-time stationary conditions. The values should be aggregated from the values for major road types in the country considered for each one indicator and weighted on the basis of traffic volume on each of these road types. Measurements should be classified according to motorways, other rural roads and urban roads.
SPIs for airbags have not been included at this stage because at present there is no Nationally available data on the number of airbags installed in vehicles.
Daytime running lights
DRL SPIs are usually considered in the form of the percentage of vehicles using daytime running lights.
The general indicator can be estimated for the whole sample of vehicles, which were observed in the country. Similar values can be calculated for different road categories and for different vehicle types.
The road categories to be considered are: motorways, rural roads, urban roads, and DRLroads, where the term “DRL roads” implies the road categories where the usage of DRL is obligatory.
The vehicle types to be considered are: cars, heavy good vehicles (including vans), motorcycles and mopeds.
In countries, where the automatic DRL was introduced long time ago (e.g. Sweden, Norway), according to expert estimates, the DRL usage rate is close to 100%, thus the DRL usage rate as a behavioural safety performance indicator does not have practical implications any more. In general, once the option of automatic DRL is introduced Europe-wide the DRL indicators will lose their importance.
Following the general concept of the DRL SPIs and accounting for current practices on the DRL use measurements in different countries possible DRL SPIs can be considered.
In total, 9 DRL SPIs are recommended for application, which are: the total usage rate and the percentages of vehicles using DRL according to four road types and according to four vehicle categories.
To estimate the above SPIs, each country should perform an annual survey of the DRL use. The details of survey will be discussed in the “Manual” document.
Passive vehicle safety
EuroNCAP is widely used as an indicator of passive safety for individual vehicles to give consumers a guide to the crashworthiness of specific makes and models. However there is no current recognised measure of an entire vehicle fleet.
For passive vehicle safety the correspondents were asked to send data containing the entire vehicle fleet database according to vehicle type, make, model and year of first registration, as it stood in 2003.
EuroNCAP scores are only currently available for passenger cars, so the present analysis concentrates on those vehicles within the national fleet. For this study it was decided that a EuroNCAP score, although describing a specific model variant, would be applied to any vehicle of the same model, to ensure a larger sample size.
For each country a EuroNCAP score was attributed to eligible vehicles. An average figure was then calculated for each year and weighted by the number of vehicles present in the 2003 fleet from that year. An overall average EuroNCAP score was then awarded for each country and together, with the median age of passenger cars in the fleet, these two figures make up the SPI for each country.
In order to validate the SPI with real-world data, car occupant fatality rates in each of the countries were considered. The number of car occupant fatalities in 2003 for each country was divided by the number of passenger cars present in each 2003 fleet, to give a figure for the number of car occupant fatalities per million cars. The average EuroNCAP score for each country was weighted by the percentage of passenger cars in a country’s 2003 fleet, which were less than 10 years old. This figure for each country was then plotted against the car occupant fatality per million cars figure for each country.
Roads
There are no direct or indirect SPIs for road networks in use in Europe at the moment. The Dutch study on quality aspects of a sustainably safe road infrastructure presented a method to assess network and design quality aspects of a safe road infrastructure at the regional level. This method could be used to formulate road network SPIs. However, the method is not commonly used yet and needs more development for use in Europe.
Even for the assessment of detailed road design there are no direct SPIs in use at the moment. Two methods could be used to formulate indirect SPIs: The Road Protection Score (RPS) of EuroRAP and the Dutch Sustainably Safe Indicator (SSI). These methods score specific road design elements. This score can be used to formulate SPIs for road design. There is some overlap in the road elements that are considered in the two methods, however the way these elements are scaled differs a lot. Both methods pay attention to homogeneity of the road traffic and forgiving road environments. The SSI has strong roots in the Dutch Sustainable Safety vision, and therefore paying more attention to the predictability of the road environment and the function in the network of the distinguished sustainably safe road
categories.
The RPS turned out to be more useful in the SafetyNet context because of two main reasons:
- all road design elements used are broadly accepted as relevant for road safety, and
- the method itself is worked out in detail and already in use in a lot of European countries.
At this stage it was considered more practical to adopt the RPS scores developed in EuroRAP as the basis for Road SPIs Europe-wide, this in view of the large amount of work already invested in the practical data collection for these RPS scores.
The assessment and weighting methods, to determine the RPS-score of EuroRAP are far more elaborately been worked out than the proposed SPI-method in the State-of-the-Art document [SafetNet 2005a]. EuroRAP has even designed a method to determine an aggregate RPS for a road. The scores for the four design elements are combined in proportion to the frequency with which the accident types matched to these design elements occurred, averaged across Sweden, Denmark, France, Hungary, Switzerland and Britain. Besides that, the potential data availability proved to be higher for EuroRAP than gathered from the questionnaire.
Therefore we propose to adopt the RPS protocol in the future so as to use and possibly share the same data as much as possible.
Nevertheless, there are three main obstacles to overcome:
- Details of the scoring and weighting methodology;
- Vulnerable road users (VRUs) are not yet included yet;
- A network approach is missing.
EuroRAP designed a method to calculate a final score for a road, expressed with one to four 'stars'. The scores on the several SPIs are weighted to calculate this final score. The magnitudes of these weights are based on accident statistics of a small and arbitrary group of European countries. Possibly these weights should depend on the distribution of accidents types in the country or region, or on the road type, where the RPS is applied. This weighting method should be as transparent as possible. SafetyNet could offer its assistance for improving this scoring and weighting method. Details of the scoring and weighing methodology are expected to be published soon.
Despite the fact that accidents with vulnerable road user are a main crash type, this item is not yet included in the RPS assessment methodology. SafetyNet could offer its assistance with defining this part of the SPI.
The 'SafetyNet Road Network SPI' enables a road authority to assess the extent to which a connection complies with the demands. EuroRAP assesses whether a road complies to design criteria. However, the EuroRAP RPS-score by itself does not indicate to which extent a road (or connection) complies with the requirements for that connection, arising from the function of the connection in the network. Therefore we propose to combine the RPS with a functional road categorization.
This will result in two aggregated network SPIs:
- Network SPI: percentage of appropriate road category (AAA-C) length per connection type (I-V);
- Road design SPI: distribution of stars (1-4) per road category (AAA-C).
Trauma management
The mechanism of post-crash trauma care (or Trauma Management – TM) comprises two types of medical treatment: that provided by emergency medical services (EMS) and that provided by permanent medical facilities.
EMS are those, which normally answer the emergency calls and deal with the next steps, like sending an ambulance to the scene of crash. EMS staff provides basic medical assistance to injured patients on the scene and during the transportation to a hospital. There are different forms of EMS, which depend on:
- the type of transport means (ambulance, helicopter);
- EMS vehicle equipment (mobile intensive care unit; basic life support unit; regular ambulance);
- medical staff arriving with the vehicle, which may include a physician, a paramedic, a “critical care” nurse, an emergency medical technician.
Further medical treatment can be provided at a regular hospital or at a specially equipped trauma centre/ the trauma department of a hospital, whereas minor injuries are usually treated by doctors/ other medical staff outside a hospital. The focus of the TM system is on patients who are hospitalized.
Based on the analysis of data available in the countries, a minimum set of the data items to be provided by the countries, was defined. These data enable the calculation of a Minimum set of Trauma Management SPIs that are necessary for an initial characteristic of the system's performance.
The minimum dataset covers seven data items as follows:
- Total number of EMS stations;
- Number of EMS staff in service (according to categories);
- Number of EMS transportation units in service (according to categories);
- The demand for a response time (min);
- Percentage of EMS responses which meet the demands for response time;
- Average response time of EMS (min);
- Total number of beds in permanent medical facilities (according to categories).
The minimum set of the TM SPIs, which can be estimated using this minimum data set, includes fourteen items as follows:
- 1. EMS stations per 10,000 citizens
- 2. EMS stations per 100 km length of rural public roads
- 3. Percentage of physicians out of the total EMS medical staff
- 4. Percentage of physicians and paramedics out of the total EMS medical staff
- 5. EMS medical staff per 10,000 citizens
- 6. Percentage of MICU out of the total EMS units
- 7. Percentage of BLSU, MICU and helicopters/ planes out of the total EMS units
- 8. EMS transportation units per 10,000 citizens
- 9. EMS vehicles per 100 km road length of total public roads
- 10.-11. Percentage of EMS responses which meet the demand for response time; to be accompanied by a data item "The demand for a response time, min".
- 12. Average response time of EMS, min
- 13. Percentage of beds in certified trauma centres and trauma departments of hospitals out of the total
- 14. Number of the total trauma care beds per 10,000 citizens
The above minimum set of TM SPIs enables to characterize both the scope and the quality of the post-crash care in the country, in terms of the EMS treatment potential (the availability and quality of resources), EMS response time and the treatment potential of permanent medical facilities (the availability and quality of resources).
According to our results, the TM system in a country can be characterized and the countries can be compared using the above described set of SPIs. However, comparing the countries it is frequently desirable to have a combined indicator which could provide an overall characteristic of the system.
Developing such a combined indicator we should emphasize that it is limited to the following considerations:
- We search for a qualitative indicator which would combine the TM SPIs' values, which are available for a country;
- A comparison by means of the combined indicator should be based on available data and then, provide an indication of "higher"/ "lower" level of the system's performance relatively to other countries in the sample;
- According to the meanings of separate SPIs, the combined indicator will tell us something about the level of the EMS treatment potential, EMS response time and the treatment potential of permanent medical facilities, i.e. the message is limited mostly to the availability of these services and, to a lesser extent, to the shares of higher-quality resources.
The combined indicator was developed by means of ranking the values of separate TM SPIs and weighting the results together. The following rules were applied:
- The combined indicator is estimated using the minimum set of trauma SPIs - 14 indicators.
- The values of each SPI should be consistent, i.e. higher values of SPIs should correspond to a better system's performance.
To avoid the dependency of the results on the estimation method and to check the sensitivity of results, three ways of ranking were applied and compared.
