Traction control system (TCS) or Anti-Slip Regulation (ASR)

A traction control system (TCS), also known as Anti-Slip Regulation (ASR), is typically (but not necessarily) a secondary function of the anti-lock braking system on production vehicles, and is designed to prevent loss of traction of the driven road wheels, and therefore maintain the control of the vehicle when excessive throttle is applied by the driver and the condition of the road surface (due to varying factors) is unable to cope with the torque applied.

The intervention can consist of one or more of the following:

• Retard or suppress the spark to one or more cylinders
• Reduce fuel supply to one or more cylinders
• Brake one or more wheels
• Close the throttle, if the vehicle is fitted with drive by wire throttle
• In turbo-charged vehicles, the boost control solenoid can be actuated to reduce boost and therefore engine power.

Typically, the traction control system shares the electro-hydraulic brake actuator (but does not use the conventional master cylinder and servo), and the wheel speed sensors with the anti-lock braking system.

Use of traction control

• In road cars: Traction control has traditionally been a safety feature in high-performance cars, which would otherwise need very sensitive throttle input to keep them from spinning the driven wheels when accelerating, especially in wet, icy or snowy conditions. In recent years, traction control systems have become widely available in non-performance cars, minivans, and light trucks.
• In race cars: Traction control is used as a performance enhancement, allowing maximum traction under acceleration without wheel spin. When accelerating out of turn, it keeps the tires at the optimum slip ratio.
• In motorcycles: Traction control for a production motorcycle was first available with the Honda ST1100 in 1992.By 2009, traction control was an option for several models offered by BMW and Ducati, and the model year 2010 Kawasaki Concours 14 (1400GTR).
• In off road vehicles: Traction control is used instead or in addition to the mechanical limited slip or locking differential. It is often implemented with an electronic limited slip differential, as well as other computerized controls of the engine and transmission. The spinning wheel is slowed down with short applications of brakes, diverting more torque to the non-spinning wheel. This form of traction control has an advantage over a locking differential, as steering and control of a vehicle is easier, so the system can be continuously enabled. It also creates less stress on the drivetrain, which is particularly important to the vehicles with an independent suspension that is generally weaker compared to solid axles. On the other hand, only half of the available torque will be applied to a wheel with traction, compared to a locked differential, and handling is less predictable.