wheels

It constantly adjusts the amount of torque to the wheels.

American drivers also have shifted to bigger vehicles with more costly creature comforts, such as heated steering wheels and vented seats.

"Modern cars are effectively computers on wheels," he said.

Last week, I stood on a Chicago street corner in a blinding snowstorm and watched a homeless man crawl inside a big wooden box on wheels.

If you get stuck, do not try to keep moving if the wheels spin - it will only dig you in deeper.