What Risk Maps Do and Do Not Show

It is important to note that risk maps based on accident rates do not show the extent to which the behaviour of a specific road-user might result in the risk being higher or lower than the average. They also do not show the extent to which the road-user can make a mistake, and recover from it without serious injury. What they do illustrate is the risk of an individual road-user, or to the community as a whole, being involved in a road accident, providing that they are behaving within acceptable boundaries of road use - for example, not intoxicated, not using a mobile phone, and obeying speed limits.

Individual risk

The public are most interested in their risk on the road as individuals. Based on real accident and traffic flow data, EuroRAP shows a road's safety performance by measuring and mapping the rate at which people are being killed and seriously injured.

For example, if over three years:

30 people are killed and seriously injured on a 30 kilometre stretch of motorway carrying 100,000 vehicles a day, and
30 people are also killed and seriously injured on a 30 kilometre stretch of single carriageway carrying 10,000 vehicles per day
then the risk to the individual is 10 times greater on the single carriageway.

Accident rates per kilometre travelled on a road can show the likelihood of a particular type of road-user being involved in an accident. Their main purpose is to inform the road-user how and where their behaviour needs to be modified to minimise risk and, in doing so, enable them to recognise the sources of risk on different types of road.

Collective risk

EuroRAP also produces maps targeted at road authorities. Collective risk maps show the density, or total number, of accidents on a road over a given length. Risk rates shown in these maps are the result of the interaction between all elements of the road system - road-users, vehicles and roads. Community risk can be mapped in three different ways:

Accident density - showing accident rates per kilometre of road, illustrating where highest and lowest numbers of accidents occur within a network.
Accident rate in relation to similar roads - comparing the accident 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 20,000 vehicles per day.
Potential for accident reduction - providing information on the number of accidents that might be saved if accident rates of road sections, with risk above the average roads of a similar flow, were reduced to the average. This information can be used for considering investment decisions, providing authorities and policy-makers with a valuable tool for estimating the total number of accidents 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.