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Status Report, Vol. 46, No. 8 | September 28, 2011 Subscribe

ESC benefits keep adding up as feature becomes standard

A new federal analysis of electronic stability control, or ESC, indicates once again that the groundbreaking safety feature is saving lives by helping to prevent rollovers and other loss-of-control crashes.

The June findings by the National Highway Traffic Safety Administration (NHTSA) update a 2007 agency report on ESC benefits (see "New data, same finding: Stability control reduces crash deaths," Oct. 13, 2007).

ESC reduces the probability that a car will be in a fatal crash by 23 percent, the agency found. The corresponding percentage for SUVs, pickups, and vans is 20 percent. Fatal single-vehicle rollover crashes are reduced even more — 56 percent for cars and 74 percent for the other vehicles. Institute research also shows benefits (see "Stability control reduces fatal crash risk by a third," June 19, 2010).

The crash avoidance technology helps drivers control their vehicles during high-speed maneuvers like entering curves or swerving to avoid obstacles on slippery roads (see "ESC reduces multiple-vehicle crashes as well as single-vehicle ones," June 13, 2006). ESC monitors vehicle response to steering and senses when a vehicle starts to stray from the intended travel path or begins to spin out. Then the system automatically brakes individual wheels and sometimes reduces engine output to keep the vehicle under control and moving in the intended direction of travel.

In the latest study, NHTSA analysts compared the crash experience of 1998-2008 passenger vehicles equipped with standard ESC and predecessor models without the feature. Fatal crash data are from 1997-2009 Fatality Analysis Reporting System files.

The agency's estimates this time around are lower than in 2007. One reason may be that the updated study included a more diverse group of vehicles than before due to the wider availability of ESC. The Institute has noted that as ESC has expanded into the general fleet of vehicles on the road, estimates of its effectiveness have declined.

Like many safety features, stability control first appeared in luxury cars and SUVs. Then in 2007 NHTSA directed automakers to install ESC in all new cars, pickups, SUVs, and vans by Sept. 1, 2011. Phase-in began with 2009 models, and most manufacturers quickly built the feature into their fleets ahead of the 2012 model year deadline.

A 2010 Institute analysis estimated that ESC is 30 percent effective in avoiding fatal crashes for cars and minivans and 35 percent effective for SUVs. It's even more effective for single-vehicle crashes. ESC's estimated effectiveness is 46 percent for cars and 53 percent for SUVs in single-vehicle crashes. For cars and SUVs combined, ESC is effective in reducing fatal single-vehicle crash risk by 49 percent and fatal multiple-vehicle crash risk by 20 percent.

Differences in estimated effectiveness between studies by the Institute and NHTSA likely are due to differing statistical methods.

"What's important," says Institute president Adrian Lund, "is that these different methods both indicate ESC is the most effective safety technology introduced in vehicles since safety belts."

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