Electronic stability control

What is Electronic Stability Control (ESC)?

Electronic stability control (ESC) is an active safety system which can be fitted to cars, buses, coaches and trucks. It is an extension of antilock brake technology, which has speed sensors and independent braking for each wheel. It aims to stabilise the vehicle and prevent skidding under all driving conditions and situations, within physical limits. It does so by identifying a critical driving situation and applying specific brake pressure on one or more wheels, as required. If necessary, the engine torque is also adjusted automatically (SUPREME).

What road safety problem does ESC address?

ESC addresses the problem of skidding and crashes due to loss of control of vehicles, especially on wet or icy roads or in rollovers.

How effective?

Evaluation studies have shown that the fitment of ESC in cars can lead to substantial reductions in crashes, deaths and serious injuries. A Swedish study in 2003 showed that cars fitted with ESC were 22% less likely to be involved in crashes than those without. There were 32% and 38% fewer crashes in wet and snowy conditions respectively [48]. In Japan, a study showed that electronic stability reduced crash involvement by 30-35% [2]. In Germany, one study indicated a similar reduction while another showed a reduction in ‘loss-of-control’ crashes from 21% to 12% [8]. UK research indicates that equipping a vehicle with ESC reduces the risk of being involved in a fatal crash by 25%. The research also shows a particularly high effectiveness for reducing serious crashes involving other loss of control situations such as skidding (33%), and rollover (59%) [23]. Research at the US Insurance Institute for Highway Safety (2006) found that ESC led to a reduction rate of 32% of the risk of fatal multiple vehicle crashes and a reduced risk of single vehicle crashes by more than 40% (of fatal ones:56%). It is estimated that equipping all vehicles with an ESC system could save over 500 deaths and 2500 serious injuries per year in the European Union alone (FIA Foundation, 2007).

Benefits to cost?

A Norwegian benefit to cost analysis considered two scenarios for ESC fitment [16]. The first was that ESC continues to be fitted gradually through the vehicle fleet, but is not made mandatory. The benefit-cost ratio in this scenario was estimated to be 4. The second scenario was ESC retrofitted on all cars of whatever age producing a benefit-cost ratio of about 0.4.

Who uses ESC now?

ESC has been on the market since 1995 and is standard equipment in many cars of the middle and upper price classes, but not yet in smaller cars. A country fitment rating is published by EuroNCAP which promotes its fitment as an important safety device. Sweden has been foremost in the national promotion of ESC and in 2006 over 90% of new cars sold in Sweden were fitted with electronic stability control.

Next steps for implementation?

An international group of experts has been set up to agree a harmonised technical specification and test method for a Global Technical Regulation (GTR) on ESC systems intended to be fitted to cars and light vans. In November 2007, the United Nations announced it would require trucks and heavy vehicles to be fitted with anti-skid Electronic Stability Control (ESC) from 2010, as a result of a new agreement reached in Geneva. The new regulation drawn up by the United Nations Economic Commission for Europe (UNECE) promotes the harmonisation of standards globally. Similar requirements for passenger cars are expected to be agreed next year.

The Australasian New Car Assessment Programme has announced that only vehicles with ESC will be given five stars from 2008 onwards. In the US, legislation was passed in 2007 making ESC mandatory standard equipment for all passenger cars, multipurpose vehicles, trucks and buses with gross vehicle rating of 4,536 kg or less from model year 2012.