ESC Technical Review
Electronic stability control (ESC) is a computerized technology that improves the safety of a vehicle’s stability by detecting and minimizing skids.
When ESC detects loss of steering control, it automatically applies the brakes to help “steer” the vehicle where the driver intends to go.
ESC does not improve a vehicle’s cornering performance, it rather helps minimize the loss of control.
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 ESC systems also reduce engine power until control is regained.
According to IIHS and NHTSA, one-third of fatal accidents could have been prevented by the technology
In 1995, automobile manufacturers introduced ESC systems. Mercedes-Benz supplied by Bosch was the first to implement this with their W140 S-Class model.
That same year BMW, supplied by Bosch and ITT Automotive (later acquired by Continental Automotive Systems), and Volvo Cars began to offer ESC on some of their models while Toyota’s own Vehicle Stability Control system (also in 2004, a preventive system called VDIM) appeared on the Crown Majesta.
Meanwhile others investigated and developed their own systems.
During a moose test (swerving to avoid an obstacle) which became famous in Germany as “the Elk test” the Swedish journalist Robert Collin of Teknikens Värld (World of Technology) in October 1997 rolled a Mercedes A-Class (without ESC) at 37 km/h.
Because Mercedes-Benz promotes a reputation for safety, they recalled and retrofitted 130,000 A-Class cars with ESC. This produced a significant reduction in crashes and the number of vehicles with ESC rose.
Today virtually all premium brands have made ESC standard on all vehicles, and the number of models with ESC continues to increase.
Ford and Toyota have announced that all their North American vehicles will be equipped with ESC standard by the end of 2009 (Toyota SUVs standard in 2004, Toyota has yet to fit the Scion tC).
However, as of 2010, both companies still sell models without ESC in North America.
General Motors had made a similar announcement for the end of 2010.
The NHTSA requires all passenger vehicles to be equipped with ESC by 2011 and estimates it will prevent 5,300-9,600 annual fatalities once all passenger vehicles are equipped with the system!
How ESC helps drivers maintain control:
A driver loses control when the vehicle goes in a direction different from the one indicated by the position of the steering wheel. This typically occurs when a driver tries to turn very hard (swerve) or to turn on a slippery road. Then the vehicle may understeer or oversteer.
When a vehicle understeers it turns less than the driver intended and continues in a forward direction because the front wheels have insufficient traction. When it oversteers it turns more than the driver intended because the rear end is spinning or sliding out.
ESC can prevent understeering and oversteering by briefly braking the appropriate wheel. In many cases engine power also is reduced.
