With AB systems, police vehicles will stop in a straight line and usually in a shorter distance than an equal-sized car without AB. An AB system will pump the locking wheel up to 10 times per second. The heart of AB is a microprocessor that senses a wheel beginning to skid and modulates brake system pressure to that wheel. The microprocessor does this by monitoring and comparing the speed of each wheel hundreds of times each second. Each wheel has a sensor that signals its speed to the brake microprocessor, and the microprocessor compares the speed of each wheel to the others. A wheel turning slower than its three partners is beginning to lock and that tells the microprocessor the brake pressure to it must be reduced. AB systems are becoming more popular as the price comes down. Chevrolet already features an AB system in a disc front, drum rear brake combination on its Caprice models. Ford will offer a four-wheel disc AB system an option on its Taurus police special and a four-wheel disc AB system and traction assist system as an option on the 1992 LTD Crown Victoria. Under normal braking conditions, there is no difference in the AB system's action or feel. In an emergency situation, however, an AB vehicle will stop smooth and straight, even with two wheels on ice. While AB systems can reduce braking distances by about 13 percent, their most important role is that of keeping a vehicle under control in emergency situations. The design of an AB system for motorcycles is examined.