Pro-Active Road Safety Engineering.
Adapted from ‘Risk’ by John Adams.
- Road users are perceptive and adaptive creatures who are constantly evaluating the dangers around them (note: danger is the potential for something to cause harm).
- Road users then act on their perceptions of danger by deciding how to balance the uncertain rewards of actions against the potential losses – how much risk they are prepared to accept (note: Risk is a decision making process that requires the balancing of uncertain rewards of actions against the potential losses).
- It is only a matter of time before a risk taken by a road user results in a loss that is significant enough to cause a road traffic collision.
- It is these losses, as a result of risks taken by road users, which are the sole cause of road traffic collisions.
- Three factors affect the distribution of road traffic collisions across the network:
Similarly, where there are more road users, and therefore more risks being taken, a road traffic collision is more likely to occur (up to a point where congestion will actually reduce the number of collisions as risks become harder to take).
Finally, road users will be more inclined to take greater risks where there is the potential for bigger rewards or where the personal risks are small (even if these risks aren’t small for other road users), increasing the likelihood of a road traffic collision.
- Therefore accident rates will be highest where actual danger exceeds perceived danger, where the concentration of road users is greatest and where potential rewards are highest or personal losses are lowest.
- But where high levels of danger are correctly perceived, such that risks taken are well informed (and therefore small), there will be no discernable change in the road traffic collision rate relative to the surrounding network.
- On the inter-urban road network we are prepared to standardise and simplify the road network by following rigid design standards, reducing conflicts and banning non-motorised modes.
- This reduces the danger of these roads for those vehicles that are left, so that they can benefit from faster speeds (and therefore shorter journey times) whilst maintaining an acceptable level of risk.
- There are two main problems with trying to design inter-urban roads in urban settings:
Roads in urban areas should perform a number of functions beyond movement – they should be characterful, legible, permeable and diverse places for a number of modes.
- We need to make a clear distinction between urban roads (the human network) and inter-urban roads (the traffic network), and adopt very different approaches to their design.
- In inter-urban settings we need to minimise danger for vehicle drivers so that they can benefit from faster journey times whilst maintaining an acceptable level of risk.
- In urban settings we need to ensure that the actual dangers associated with taking risks are kept low, especially for the most vulnerable road users, whilst providing vehicle drivers the right clues about expected behaviour and the consequences of risk taking.