A Warning Light When ESC Is Active? Who Needs it!

Warning lights and telltales generally share one thing in common: they activate when there is a problem with a vehicle function with one exception: the Electronic Stability Control (ESC) or Slip indicator. It is seen when the system is activated and doing its job as well as when there is a problem. That is, just when a vehicle detects excessive stress at the front or rear wheels that could lead to a loss of control, the light begins to flash on the instrument panel.


slip_indicator_symbolSo, while one result is that the vehicle is more likely to remain in control, another is that the driver’s attention is taken off the road! Given the recent emphasis on reducing distracted driving, this would seem to be more than a bit counter to the cause.

So we set out to find out why. What we discovered was more than surprising. The National Highway Traffic Safety Administration (NHTSA), which makes the rules, had very similar concerns and studied the issue. In the end, we still don’t know why the warning light is allowed to come on when ESC is in operation, since it turns out not to be required. Here are the pertinent results.

NHTSA conducted the study using the National Advanced Driving Simulator (NADS). They used 200 participants in four age groups, simulating driving on wet pavement. The experiments used road departures and eye glances to the instrument panel to measure a driver’s performance. They were given either no indication of ESC activation, a steady-burning icon, a flashing icon, or an auditory warning.

The auditory warning led to 15% more road departures than participants receiving only visual indications (steady 8%, flashing 8%) or no ESC activation indications (7%). Younger drivers fared somewhat better than older drivers (ages were not given).

Further, the results showed that participants given a flashing telltale glanced at the instrument panel 14% more frequently than when given a steady light or and auditory only signal, which was statistically significant and exactly what we anticipated (the study found “there was no measurable consequence in road departures”).


So, the study done by the NHTSA finds that the least number of road departures occurred when no indication of ESC activation was given! The difference is slight, but exists and no glance to the instrument panel accompanies the activation of ESC. So, no distraction. In fact, the NHTSA’s own conclusion is that “there does not appear to be a safety need to propose a requirement for an ESC activation indicator as part of this rulemaking, and none is proposed.”

So, there is no requirement for the ESC telltale to be active when the system is doing its job. Simple intuition suggests that when stability control is needed, a driver needs all his or her attention on the act of driving. And let’s remember that a mere 200 drivers Stabilty Control Fault Indicatorare being used to represent the reactions of millions.

With that we say to all manufacturers, keep the ESC indicator off when its doing its job! And to the NHTSA, make this the rule!


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