Potential Effects of Electronic Stability Control (ESC) on Accidents
Alena Erke, Institute of Transport Economics, NO
Potential effects of ESC on accident frequency and severity are estimated by a literature survey, analysis of accident statistics, and metaanalysis. Technical developments, ergonomic requirements, and methodological aspects are discussed.
Electronic Stability Control (ESC) is an active safety device for motorvehicles. ESC enhances controllability, and can prevent skidding in cases of oversteering or understeering. Accidents involving skidding can be prevented, or accident severity can be reduced due to reduced probability of side collisions and roll-overs. Additionally, ESC can influence driver behaviour by informing about low-friction driving conditions.
Based on a literature analysis, accident statistics and a review of in-depth accident analyses it is estimated which proportions of different types of accidents might be influenced or prevented with ESC. The total amount of ?potentially influenceable? accidents can be seen as the theoretical maximum for accident reducing effects of ESC. A relatively large amount of single accidents have potential to be influenced by ESC, and a smaller amount of accidents involving several vehicles. However, not all accidents that may be influenced by ESC can be prevented, but may have less serious consequences. Limiting and enhancing factors for the effectiveness of ESC include type of vehicle, road design, weather, driver behavior, tyres, load, brakes and chassis frame.
A metaanalysis is conducted which includes studies that have investigated number and type of accidents involving cars with and without ESC. All studies have found reductions in single accidents for cars with ESC. On the average, effect sizes correspond to the estimated maximum for single accidents, but differ depending on how accurate the studies controlled for other simultaneous improvements of active or passive safety. As the estimated maximum is an upper limit for influenceable accidents, not for the total amount of preventable accidents, this effect ist likely to be overestimated. For multi-vehicle accidents, no effects of ESC are found in the metaanalysis, even though accident analyses have shown a potential.
In summary, the results show a considerable potential of ESC to prevent accidents and reduce accident severity. Differences between estimates from different methods (analysis of accident reports and statistics vs. metaanalysis) and for different accident types suggest the presence of interaction effects between ESC and other factors, namely driver behaviour and other active and passive safety systems.
Based on the combined results, it will be discussed in what way ESC affects the road-vehicle-driver system. Further improvements of vehicle safety could be achieved by combining ESC with other in-vehicle safety systems (braking assistent, steering assistent, integrative cruise control). Improvements in vehicle safety could be supplemented by road safety measures aiming at improving adaptation of driver behaviour to driving condition by visual (e.g. road markings, chevrons, road studs) or vibratory (rumble strips) guidance. Finally, ESC is likely to affect driver behaviour, and system-design should be such as to prevent risk-taking behaviour and to improve adaptation to driving conditions.
Association for European Transport