Diagram & Summary
Speeding: more and more severe accidents
Speed is at the core of the road safety problem. In fact, speed is involved in all accidents: no speed, no accidents. In around 30% of the fatal accidents speed is an essential contributory factor. Firstly, speed affects the risk of being involved in an accident. At a higher speed, it is more difficult to react in time and prevent an accident. Secondly, speed affects the injury consequences of an accident. At a higher (impact) speed, more energy is released when colliding with another vehicle, road user or obstacle. Part of this energy will need to be absorbed by the vulnerable human body. Very strong relationships have been established between speed and accident risk and severity.
Excess speed and inappropriate speed are very common
Speed limits provide information to the drivers about the safe speed to travel in average conditions. Exceeding the speed limits is very common. Typically, 40 to 50% of the drivers travel faster than the speed limit. Typically, 10 to 20% exceed the speed limit by more than 10 km/h. In addition, drivers adapt their speed insufficiently to local and temporary conditions related to traffic and weather. They often choose a speed that is inappropriate for the prevailing conditions. Speed choice is related to the drivers' motives, attitudes, risk perception and risk acceptance. Furthermore, speed choice is affected by characteristics of the road and the road environment and by characteristics of the vehicle.
What to do? Countermeasures as a package
There is no single solution to the problem of excess and inappropriate speed. A package of countermeasures is necessary, increasing the effectiveness of each of the individual measures. The most appropriate combination of measures will differ with circumstances. As a start, a good balance between road design, speed limit, and public perception of appropriate speed is vital.
At the core of speed management are the speed limits. Speed limits must define a safe speed, reflecting the function of the road, traffic composition and road design characteristics. Speed limits must also be credible, reflecting the characteristics of the road and the road environment. Drivers must be aware of the local speed limit at all times. This can be realised by good and consistent signing as well as consistent application of road markings and delineation, specifically related to particular speed limits.
Road engineering, such as speed humps and narrowings, helps to reduce speed at locations where low speed is essential. If applied in a consistent way, these measures also help drivers to recognize the traffic situation and the corresponding speed limit. Despite these measures, there always will be drivers who exceed the speed limit. For these intentional violators enforcement remains a necessary instrument. Speed management has to be accompanied by education and information to make road users aware of the speed and speeding problem and about the 'why' and 'what' of countermeasures.
And what about new technologies?
New technologies enable in-vehicle systems that support drivers to comply with the speed limits. These systems provide information about the speed limit in force; warn the driver when exceeding the limit; or make excess speed impossible or uncomfortable. Such systems are available and likely to be introduced progressively. New technologies also enable communication between road and vehicle, allowing for full dynamic speed limits, based on the actual traffic and weather conditions. These systems are still under development.