On these surfaces, locked wheels dig in and stop the vehicle more quickly. In gravel and snow, ABS tends to increase braking distances. In such situations, ABS will significantly reduce the chances of a skid and subsequent loss of control. The recommended technique for non-expert drivers in an ABS-equipped car, in a typical full-braking emergency, is to press the brake pedal as firmly as possible and, where appropriate, to steer around obstructions. However, for a majority of drivers, in most conditions, in typical states of alertness, ABS will reduce their chances of crashing, and/or the severity of impact. An alert skilled driver without ABS should be able, through the use of techniques like cadence braking or threshold braking, to match or improve on the performance of a typical driver with an ABS-equipped vehicle. shorter) than those that would be easily possible without the benefit of ABS. On high-traction surfaces such as bitumen, whether wet or dry, most ABS-equipped cars are able to attain braking distances better (i.e. The sensors can become contaminated with metallic dust and fail to detect wheel slip this is not always picked up by the internal ABS controller diagnostics.ġ The electronic unit needs to determine when some of the wheels turn considerably slower than any of the others because when the car is turning the two wheels towards the center of the curve inherently move slightly slower than the other two - which is the reason why a differential is used in virtually all commercial cars. When it senses that any number of wheels are rotating considerably slower than the others (a condition that will bring it to lock 1) it moves the valves to decrease the pressure on the braking circuit, effectively reducing the braking force on that wheel and causing a characteristic pulsing feel through the brake pedal. The electronic unit constantly monitors the rotation speed of each wheel. The anti-lock brake controller is also known as the CAB (Controller Anti-lock Brake).Ī typical ABS is composed of a central electronic unit, four speed sensors (one for each wheel), and two or more hydraulic valves on the brake circuit. The first car (worldwide) to have ABS fitted as standard (across the entire range) was the Ford Granada Mk 3 (of 1985). It saw limited automobile use in the 1960s, but saw no further use the system proved expensive and in automobile use somewhat unreliable. An early system was Dunlop's Maxaret system, introduced in the 1950s and still in use on some aircraft models. Systems were later introduced on motorcycles.Īnti-lock braking systems were first developed for aircraft. They first appeared in trucks and German limousines from Mercedes-Benz. The German firm of Robert Bosch GmbH had been developing anti-lock braking technology since the 1930s, but the first production cars using Bosch's electronic system became available in 1978.
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