Safety Technology: ESP

Electronic Stability Programme (ESP) is known by different product names, depending on the preference of the vehicle manufacturer.  Innovation of this technology came about 1987 as development of Anti-lock Braking (ABS) and traction control systems.

ABS enables ESP to brake on individual wheels. ESP systems often incorporate a traction control system, which senses drive-wheel slip under acceleration and individually brakes the slipping wheel or wheels and/or reduces excess engine power until control is regained.

During normal driving, ESP operates in the background, continuously monitoring steering and vehicle direction. ESP compares the driver's intended direction (by measuring steering angle) to the vehicle's actual direction (by measuring lateral acceleration, vehicle rotation (yaw) along with individual road wheel speeds).

ESP intervenes when it detects loss of steering control, that is, when the vehicle is not going where the driver is steering. ESP automatically applies the brakes to help "steer" the vehicle where the driver intends to go. Braking is automatically applied to individual wheels, such as the outer front wheel to counter oversteer or the inner rear wheel to counter understeer. Some ESP systems also reduce engine power until control is regained. Electronic stability control does not improve a vehicle's cornering performance; rather it helps to minimise a loss of control.

Many ESP systems have an "off" override switch so the driver can disable ESP, which may be desirable when badly stuck in mud or snow, or driving on a beach, or if using a smaller-sized spare tyre which would interfere with the sensors. Some systems also offer an additional mode with raised thresholds so that a driver can utilize the limits of adhesion with less electronic intervention. However, ESC defaults to "On" when the ignition is re-started.

ESP works on all road surfaces.  It reacts to and corrects skidding much faster and more effectively than the typical human driver, often before the driver is even aware of any imminent loss of control.

There are some concerns that ESP can make drivers to become overconfident of their vehicle's handling ability and their own driving skills. ESP systems therefore will inform the driver when they intervene, so that the driver knows that the vehicle's handling limits have been reached. Most activate a dashboard indicator light and/or alert tone.  Manufacturers emphasise that the system is not a performance enhancement nor a replacement for safe driving practices, but rather a safety technology to assist the driver in recovering from dangerous situations.