electronic stability control

Electronic Stability Control (ESC) is one of the latest vehicle safety technologies aimed at preventing crashes. Recently, several studies have found that ESC is very effective at reducing crash and fatality rates by helping drivers to maintain control of their vehicles.

RACV position

RACV encourages vehicle manufacturers to fit ESC as a standard feature.
RACV encourages private and fleet car buyers to specify a vehicle equipped with ESC.
RACV calls on vehicle manufacturers to adopt a common name to refer to the technology to avoid consumer confusion with the product.

findings of international research into ESC

IIHS study

The US based Insurance Institute of Highway Safety studied the effectiveness of stability control as a road safety measure. The study released in October 2004, found that the fitment of ESC was effective in reducing single vehicle crashes including those involving fatalities. The US study showed that based on all police-reported crashes in seven states over two years, ESC was effective in reducing fatal crashes by 34 percent.

swedish study

A Swedish National Road Administration study (2003) reported ESC effectiveness levels in different conditions on Swedish roads. They found that the effectiveness of ESC in reducing crashes was around 22 percent. In wet and snow conditions the reductions attributed to ESC were even higher.

daimler chrysler claims

Daimler Chyrsler claim that "The average share of newly registered Mercedes models involved in such (single vehicle) accidents in 1998/1999 was 20.7 percent. ESP® (ESC) helped to reduce this figure by more than 42 percent in 2002/2003. At the same time, the share of passenger car models from other brands involved in these types of traffic accident fell by only about 13 percent."

The IIHS study found that ESC benefits are most prevalent in single vehicle crashes. Examples of single vehicle crashes include impacts involving a roll over and impacts with rigid objects such as trees. In Australia, single vehicle crashes accounted for 399 fatalities in 2003 (44 percent of total fatalities), more than the number of fatalities from multiple vehicle crashes.

how stability control works

components

ESC builds on the components already attached to the vehicle for ABS brakes and traction control. It uses the wheel speed sensors and the ability to apply brake pressure to individual wheels but adds a steering angle sensor and a sensor that detects the direction of the vehicle. Some advanced systems also have body roll sensors that add more sophistication to the system.

function

ESC continuously compares the driver's commands to the actual direction of travel of the vehicle. When the control unit detects a discrepancy, ESC intervenes by automatically applying the brakes to an individual wheel. In some cases, it will reduce the engine power as well. The intervention of ESC helps the driver to maintain control of the vehicle.

Some ESC systems will intervene sooner than others. Other vehicles are fitted with switches that either delay or completely remove intervention.

when do you lose control?

ESC starts to intervene when the vehicle travels on a different course than that intended by the driver. 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.

Understeer can be described as when the vehicle does not turn as much as the driver intended. This occurs because the front wheels have lost traction with the road. Oversteer is the opposite. It occurs when the vehicle turns more than the driver intends because the rear wheels have lost traction with the road. See Figure 1. Figure 2 compares these two events and shows how ESC applies the brakes to help the driver maintain control.

what is the difference between ESC, ABS and traction control?

Where ABS and traction control were effective in assisting with braking and acceleration, the addition of the extra sensors enables ESC to offer the driver assistance in turning under hazardous conditions. As road safety measures go, ABS has not proven to be as effective a measure in preventing crashes. RACV's report on the real world performance of ABS brakes found that vehicles equipped with ABS brakes had a some what higher risk of involvement in single vehicle crashes. Vehicles equipped with ESC will also feature traction control and ABS brakes.

Vehicle equipment	Situation
Traction control	This systems prevents wheel spin under acceleration which helps to maintain steerability when accelerating
ABS	ABS helps a driver to prevent skidding during heavy braking. This will help to maintain steering control and achieve shorter braking distances
EBD	helps to balance braking forces between front and rear. In turn this helps to minimise braking distance and keep stability under light axle loads.
ESC	Builds on all the functions above but adds the ability to control skidding during cornering as well.

other names for ESC

Potentially confusing for consumers, ESC has a wide variety of marketing names for what is essentially the same function. ESC names include:

Electronic stability program (ESP)
Vehicle stability control (VSC)
Dynamic stability control (DSC)
Vehicle stability assist (VSA)

when did it first appear?

ESC was first introduced in the European market in 1995. It has since spread to Australia and is now a standard feature on many luxury makes. Now, ESC has made its debut in Australian built cars such as the all wheel drive Ford Territory. It has since become available in the Holden Commodore Acclaim.

Stability control as an option can cost anything between $500 and $2,600 as an option depending on the make and model of the vehicle.

For further information:

Email: care@racv.com.au