photo: fortes
In my last post regarding Winter Driving, I failed to mention what is probably the most important technology in keeping you out of an accident when driving in the snow. Its known by many names, but generically it is usually referred to as Electronic Stability Control.

What is Electronic Stability Control? Generally speaking it is a computer oversight of the cars current traction situation, and the ability of the computer to override the driver’s control of the accelerator in order to restore a lost traction situation.

The easiest way to demonstrate electronic stability control is to simply stomp on the gas from a standing start in a car that has the feature turned off - the wheels will spin until they warm up and get some traction from forward motion, and you will hear the engine roar as you dump all that fuel into it.

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If you turn the feature on and do the same thing, something very unexpected will happen - the engine will not roar, the tires will not spin. Instead, the car will move forward, cutting and enabling the engine power and/or brakes only to the point where the tires lose traction. No additional force is applied, and the tires stay on the road.

Its not a completely smooth experience, as the adjustments are somewhat abrupt.

In a similar situation more akin to the problem domain Electronic Stability Control seeks to solve in the first place, the driver takes a corner at speed in the rain - with ESC off in a RWD drive vehicle, the rear wheels will ‘fishtail’ or oversteer to some degree depending on the speed, turn, and driver input. With ESC the fact that the car is not travelling in the direction the driver is pointing the steering wheel enables the system and power and brakes are adjusted to compensate.

Just like your first time driving with cruise control, ESC kicking in can be a very surprising event for the driver - especially since most conservative drivers may go years without even having it happen. Its one of those ‘whoa I am not controlling the car’ moments - but in every case you learn to avoid it - to keep the car under control - and in this light ESC kind of serves as a gentle safety teacher.

ESC is the perfect complement to AWD and Winter Tires. Whereas Winter Tires and AWD seek to improve traction, ESC specifically takes over when traction is lost - providing a continuation of safety where the other two leave off. Similarly, the winter tires and awd reduce the necessity of ESC coming on in the first place.