Wednesday, January 19, 2005

Computers Drive Better Than People

by Tom Bozzo

More precisely, electronic stability control systems are astonishingly effective at helping drivers avoid single-car accidents, according to studies by NHTSA and IIHS. (Via Car and Driver.)

The systems, which work in conjunction with anti-lock braking systems to better translate drivers' intentions into the actual direction of travel*, reduce the risk of single vehicle accidents by roughly 40%, and reduce fatal single vehicle accidents as much as 56% by the IIHS reckoning.

If stability control systems — equipped on 7.4% of 2003 new cars — were in universal use, several thousand fewer traffic deaths would occur annually. As this would eventually cost about $1.2 million per life saved**, it would appear to pass cost-benefit muster. Much wider deployment, as well as autonomous reductions in electronics costs, would probably lead to large reductions over time in the current $500 cost of the systems and thus widen the benefit-cost gap.

As a snow belt owner of a rear-drive car with all-season tires and electronic stability control, and now further as a resident of a street that is low on the city's snow clearing priorities, I can attest to the often uncanny effectiveness of the systems.

SUV detractors might note that the NHTSA study shows double the effect of stability control on total and fatal crash rates for SUVs versus cars — a 67 percent single-vehicle accident rate reduction. This has a lot to do with the tendency of SUVs to roll over when they depart the road out of control, but also speaks volumes as to the fundamental controllability shortcomings of SUVs.

There are some uncontrolled factors that the NHTSA researcher suggests might increase the measured effectiveness of stability control for SUVs, notably higher seat belt use in the stability control group. However, the bulk of the SUVs equipped with stability control for the study were Lexus RX300 and Mercedes M-class models, which are arguably among the better-handling SUVs to begin with. So I wouldn't be surprised if the stability control effect weren't bigger in truck-based SUVs with primitive suspension systems and relatively high centers of gravity.

* Provided the driver doesn't expect stability control to repeal the laws of physics, as the systems' legal disclaimers note.

** Based on the current $500 cost to equip each of 17 million new vehicles annually, and 7000 fewer annual fatalities.
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