Funding Organisation: Department for Transport
Intelligent Speed Adaptation (ISA) is one of the most promising Intelligent Transport Systems in terms of its potential impact on safety. It is a system by which the vehicle “knows” the permitted or recommended maximum speed for a road. The standard system uses an in-vehicle digital road map, onto which speed limits have been coded, combined with a vehicle positioning system, such as satellite GPS. The study will be designed to quantify how ISA might affect a driver’s overtaking decisions on rural roads. The study will use the new, full motion, University of Leeds Driving Simulator and allow the presentation of a variety of overtaking scenarios in a safe and controlled environment. The accident rate associated with UK rural roads is relatively high, compared to that of urban and motorway environments. Motorways are five times safer than the average single-carriageway road and twice as safe as dual-carriageways. This is often attributed to lower standards of road design and higher occurrences of overtaking and run-off-the road accidents. A system, such as ISA, that restricts the maximum may have general “calming” benefits for rural roads, however accidents are more commonly associated with poor overtaking decisions and inappropriate curve negotiation speeds (which are usually lower than the posted speed limit). Attempting to reduce the number of erroneous overtakings is the preferred route, but it should be recognised that some drivers will always wish to engage in such behaviour, even when the perceived risk is relatively high.