The concept for ABS dates back to 1908, when J.E. Francis introduced his 'Slip Prevention Regulator for Rail Vehicles'. Gabriel Voisin experimented with systems modulating hydraulic braking pressure on aircraft in 1920 to reduce tire slippage. Karl Wässel’s system for modulating braking power was patented in 1928, though he never developed a working product. By the early 1950s, the Dunlop Maxaret anti-skid system was in widespread aviation use in the UK, fitted to aircraft such as the Avro Vulcan and Handley Page Victor. A fully-mechanical system saw limited automobile use in the 1960s in the Ferguson P99 racing car, the Jensen FF, and the experimental Ford Zodiac. The modern ABS system was invented in 1971 by Mario Palazzetti at the Fiat Research Center and was later named ABS by Bosch.
Modern ABS systems typically include an electronic control unit (ECU), wheel speed sensors, and hydraulic valves. The ECU monitors wheel speed, and if it detects a wheel rotating significantly slower than the vehicle speed, it actuates the valves to reduce hydraulic pressure to that brake. In 1985, the Ford Scorpio was introduced with a Teves electronic system throughout the range as standard, and was awarded European Car of the Year in 1986. Since 1987, ABS has been standard equipment on all Mercedes-Benz automobiles.
A 2004 Australian study by Monash University Accident Research Centre found that ABS reduced the risk of multiple vehicle crashes by 18 percent. However, the same study found ABS increased the risk of run-off-road crashes by 35 percent. A June 1999 NHTSA study found that ABS increased stopping distances on loose gravel by an average of 27.2 percent. The Insurance Institute for Highway Safety released a study in 2010 that found motorcycles with ABS were 37% less likely to be involved in a fatal crash than models without ABS.
Motorcycle ABS prevents wheel lock during braking, adjusting brake fluid pressure based on wheel speed sensors to maintain traction. Different approaches to motorcycle ABS include systems with and without active pressure build-up, with some allowing riders to adjust braking behavior. The EU mandated ABS on all new motorcycles above 125cc from 2016, following studies indicating its safety benefits.
ABS utilizes different schemes depending on the brake type, differentiated by the number of channels and sensors. These include four-channel, four-sensor ABS, three-channel, four-sensor ABS, and one-channel, one-sensor ABS. The components of ABS include speed sensors, valves, a pump, and a controller. Speed sensors use magnets and Hall effect sensors, or variable reluctance sensors, to generate a signal based on wheel rotation. Valves control brake pressure, with three positions: open, blocked, or releasing pressure. The pump restores pressure after the valves release it, and the controller receives information from the wheel speed sensors to regulate the system.
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