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Ask the Editor: What Is Stability Control?

Stability Control reduces the risk of losing control during abrupt maneuvers at speed.

A reader emailed us and asked what a stability control system is. Here’s the scoop:

Stability control is a system that helps the driver stay in control of the car during abrupt changes of direction. In basic terms, when you swerve, the stability control system in your car keeps you in control. Stability control is often referred to as electronic stability control. Different automakers also give ESC different names like AdvanceTrac, StabiliTrac, Vehicle Stability Assist and Vehicle Dynamics Control.

Imagine driving down the highway following a car carrying a mattress on its roof. The mattress falls off, but you don’t have time to brake, so you swerve into the other lane to avoid it. In that situation, the big risk (other than hitting the mattress) is that the quick change in direction while traveling at highway speeds will cause one or more of your tires to lose traction. If that happens, you could go into a skid, which drastically increases your odds of losing control of your car and colliding with something. The Insurance Institute for Highway Safety says that stability control reduces the risk of single-vehicle crashes by 40 percent and the risk of fatal single-vehicle crashes by 56 percent.

Stability control works to maintain control, constantly monitoring the traction of individual wheels. It also monitors the driver’s steering inputs. Using that information, the system can apply the brakes to individual wheels to help keep the car in control and on its intended path. Stability control not only helps drivers maintain control in emergency maneuvers like swerves, but also in extreme cornering situations.

Stability control is often coupled with anti-rollover systems, especially in SUVs. With roll stability control, the system not only detects and works to prevent impeding skids, but it also can detect impending rollovers and work to prevent them. If a rollover can’t be prevented, the system lets other safety systems in the car know, so the car can roll up the windows, tighten the seatbelts, deploy the airbags and do a better job of protecting the occupants.

Stability control also helps maintain control in cornering.

Traction control is also frequently partnered with stability control. Since stability control works to maintain traction during turns, it’s easy to get the two confused. Traction control, however, is more similar to anti-lock brakes than stability control. While anti-lock brakes help maintain traction while you’re slowing down, traction control maintains traction while you’re accelerating, especially on slippery surfaces. Though traction and stability control often work together, they’re technically two separate systems.

For 2012, all cars, SUVs and light-duty trucks sold in the U.S. will be required to have ESC. The National Highway Traffic Safety Administration estimates that this requirement will reduce the number of single-vehicle crashes involving cars by 34 percent and the number of single-vehicle crashes involving SUVs by 59 percent. NHTSA also estimates that the new requirement will cut the number of rollovers by 71 percent in cars and 84 percent in SUVs. All told, NHTSA says the requirement could save anywhere from 5,300 to 9,600 American lives each year and prevent 156,000 to 238,000 injuries.

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