<Dd> There is a speed sensor on all four wheels and a separate valve for all four wheels . With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force . </Dd> <Dt> 2) Three - channel, four - sensor ABS </Dt> <Dd> There is a speed sensor on all four wheels and a separate valve for each of the front wheels, but only one valve for both of the rear wheels . Older vehicles with four - wheel ABS usually use this type . </Dd> <Dt> 3) Three - channel, three - sensor ABS </Dt>

When did abs become standard in the us