Cars with ESC involved in 3% fewer crashes, 25% fewer on snowy & icy roads.

Proceedings, 13th ITS World Congress and Exhibition

8-12 October 2006, London, UK

Overall the cars with ESC are involved in 3% fewer crashes although the effectiveness is substantially higher under conditions of adverse road friction i.e. 25% reduction on snowy and icy roads. ESC equipped cars are involved in 15% fewer fatal crashes although this reduction represents the combined effect of ESC and passive safety improvements.

The study used the national accident statistics of Great Britain. The crash experience of 8951 cars was analysed and compared to a closely matching set of non-ESC cars using case-control methods.

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Crabsallover Comments: These results are often statistically not significant and sometimes its not clear which results are significant and which are not. The graphs should highlight these differences in signficance, but do not.  This analysis of GB national accident data has indicated that cars equipped with ESC are involved in 3% fewer crashes overall compared to unequipped cars. This compares to 22% effectiveness in Sweden and 45% in Germany using similar methods. The UK ESC effectiveness results are an order of magnitude lower than those in Germany or Sweden - the report does not explain why there should be such a huge difference in the UK, Swedish and German results. The analysis has shown that ESC is most effective under poor road surface conditions such as rain, snow and ice where the effectiveness increases to 25%. The data also indicates that these conditions are relatively rare in Great Britain with only 2% of crashes taking place on snow or icy roads (but I doubt these conditions are an order of magnitude greater in Sweden or Germany).

Overall the cars with ESC are involved in 3% fewer crashes although the effectiveness is substantially higher under conditions of adverse road friction. ESC equipped cars are involved in 15% fewer fatal crashes although this reduction represents the combined effect of ESC and passive safety improvements. 

The final dataset comprised 890,648 cars of which 8,685 were equipped with ESC.... The data was for 2002 – 2004. The UK Accident Data records the severity of the injuries sustained in the crash. Fatal crashes include at least one casualty that has died within 30 days of the crash, seriously injured casualties have sustained at least a fracture or have been detained in hospital at least overnight while slightly injured casualties have sustained lower severity injuries, normally lacerations and contusions. The reductions of these casualties in vehicles equipped with ESC are shown in Figure 2 for all crashes, crashes where a car occupant was either killed or seriously injured (KSI) and fatal crashes. Overall ESC equipped cars were involved in 3% fewer crashes than non-equipped vehicles but KSI crashes were 19% lower and fatal crashes were 15% lower, although this result was not statistically significant.

On snow or icy road conditions ESC equipped cars had substantially fewer crashes. Overall there were 25% fewer crashes while KSI crashes were reduced by 53%. There were insufficient cases to evaluate fatal crash reductions of ESC fitted vehicles.

Frontal collisions of all severity levels were 10% lower in ESC equipped cars while side impacts reduced by 7%. KSI crashes were 18% lower in collisions to the front of the car and 28% lower in side crashes. Fatal crashes were 38% higher in ESC equipped cars in side impacts although there were insufficient cars to evaluate changes in frontal fatalities. None of these differences between front and side impact was statistically significant as was the apparent increase in fatalities.

Small family cars showed a non-significant increase in crash rates of 2% for the ESC equipped cars while large family cars had a 13% lower crash rate. Large off-roaders showed a 24% increase in crash rates. Small MPVs, with just one model of car, showed a 74% lower crash rate while large MPVs with 2 models showed a 29% increase.

DISCUSSION This analysis of GB national accident data has indicated that cars equipped with ESC are involved in 3% fewer crashes overall compared to unequipped cars. This compares to 22% effectiveness in Sweden and 45% in Germany using similar methods. The analysis has shown that ESC is most effective under poor road surface conditions such as rain, snow and ice where the effectiveness increases to 25%. The data also indicates that these conditions are relatively rare in Great Britain with only 2% of crashes taking place on snow or icy roads.

Although the benefit to Great Britain from ESC does not appear to be as large as in other countries with more frequent adverse road surface conditions it is nevertheless still significant in financial terms. In 2004 there were 292,000 cars involved in crashes in GB, most of which were not equipped with ESC, these results indicate that if they had been there would have been nearly 9,000 fewer crashes. The UK Department for Transport has estimated the average cost of a crash to be £62,197 in 2004 values10 so the total saving resulting from uniform fitting of ESC to cars is £544,845,720 (€730,093,265).

CONCLUSIONS This analysis of the GB national accident data has shown that cars equipped with electronic stability control systems have a lower crash involvement rate than non-equipped cars. The overall reduction for crashes of all injury severity is 3% but on icy roads or snow this rises to 25% but the accident data shows that only 2% of crashes occur under these conditions.