The Toyota Mark X is driven to demonstrate its VGRS safety system. VGRS, which stands for variable gear ratio steering, controls steering, braking and turning of the tires to reduce spinning and skidding when braking and turning on slippery surfaces.

AP Photo/Koji Sasahara

Where the Rubber Meets the Road … and the Electronic Sensors

The scientists behind the first traction control systems weren't completely mad. Actually, they were probably boringly task-oriented and striving to meet performance goals in some lovely corporate building with vacation time and benefits and nary a pair of black rubber gloves in sight. That's fine, engineers. Be that way. Readers will have to supply their own mad cackling while reading how traction control works.

So, living in the twenty-first century means that your car has a computer. It also means that your car probably uses a drive-by-wire system, which means there's no mechanical connection between the gas pedal and the throttle mechanism; pressing the accelerator pedal sends an electronic signal to the throttle, and it speeds up the car. And having ABS means that you have speed sensors at each wheel tracking how fast the wheel is turning; the computer compares all four wheel speeds to see if one of them isn't doing its job. In the case of ABS, it's making sure one of the wheels isn't locked up and sending you skidding into a ditch. With a traction control system, those same electronics make sure the wheels are all turning at the same speed compared to the road. It'll determine if a wheel is slipping -- you know, spinning faster than the other wheels, all wild and crazy-like. A cackle might work here, if you choose.

The car's computer has a couple of choices to make, and what it picks depends on how it was programmed and what the conditions are. Often, the computer will apply the brakes just a little bit to slow that out-of-control tire down until the tread can get some bite on the road and prevent it from slipping. If further steps are required, traction control can even reduce engine power and torque until the tire slows down enough to get a grip. A cackle here might be inappropriate.