Electronic stability control (ESC) is a crash avoidance technology that continuously monitors how well a vehicle responds to a driver's steering input and selectively applies the brakes and modulates engine power to keep the vehicle traveling along the intended path. ESC first appeared primarily in luxury vehicles; it now has filtered down to the general fleet. Multiple studies and intensive testing have reported the benefits of ESC, resulting in the National Highway Traffic Safety Administration (NHTSA) issuing regulations requiring all passenger vehicles manufactured after September 1, 2011 for sale in the United States to be equipped with ESC. This study, published by the Insurance Institute for Highway Safety, looks at the effectiveness of ESC on fatal crashes for the general fleet of passenger vehicles.
The vehicle models included in this study were general fleet vehicles that changed from no ESC available in one model year to ESC as standard equipment in the next model year without any other significant design changes. Model years were restricted to, at most, the last 4 years without ESC and the first 4 years with ESC. The fatal crash records were extracted from the 1999-2008 files of the Fatality Analysis Reporting System. Expected crash counts were computed for ESC versions of each of the relevant vehicle models . The expected crash count for the ESC version is the product of the crash rate for the pre-ESC version and the registration count for the ESC version. The risk ratio was defined as the sum of the observed crash counts for ESC vehicles divided by the sum of the expected counts. Thus, a risk ratio significantly less than 1 could be taken as evidence that ESC reduces fatal crash risk.
- Based on all fatal crashes in the United States during 10 years, ESC was found to have reduced fatal crash involvement risk by 33 percent (20 percent for multiple-vehicle crashes and 49 percent for single-vehicle crashes).
- Although not statistically significant, effectiveness estimates were higher for SUVs than for cars ( 35 percent for SUVs and 30 percent for cars).
- Fatal crash involvement risk was reduced by an estimated 2 percent for full-size vans equipped with ESC, but this estimate was based on relatively little data and was not statistically significant.
- ESC was estimated here to have greatly reduced the risk of a fatal crash. However, the estimated reduction of 33 percent is lower than that of some earlier studies.
- ESC leads to reductions especially for fatal single-vehicle crashes, but there also are reductions for fatal multiple-vehicle crashes.
- There were no clear differences in effectiveness across automakers.