Mercedes-Benz S-class
In Europe, the Mercedes S-class uses Adaptive Brake Light technology that flashes brake lights if the car is brought to a stop from a very high speed.
By Roland Jones Business news editor
updated 2/17/2006 9:18:22 AM ET 2006-02-17T14:18:22

Ever since Nicolas-Joseph Cugnot crashed his “fardier à vapeur,” or “steam wagon,” into a wall in the late eighteenth century, inadvertently creating the first recorded automobile accident, safety has been paramount for vehicle makers.

Carmakers have developed everything from antilock brakes to airbags in an effort to make driving safer and reduce the harmful effects of road accidents. And now Mercedes-Benz USA wants to take road safety one step further.

In January, National Highway Traffic Safety Administration awarded the U.S. subsidiary of the German luxury car company a temporary exemption from U.S. automobile safety standards, allowing it to sell as many as 5,000 vehicles over the next two years that include brake lights that flash during emergency stops.

The NHTSA had originally refused to make a permanent change to its auto safety rule, which requires the steady illumination of vehicle lights, but relented when Mercedes said it wanted to show its flashing brake lights improve car safety by preventing rear-end crashes. Dubbed Adaptive Brake Lights, these brakes lights are only activated when the brake pedal is pushed heavily for a hard stop. The feature is already available in Europe in Mercedes S-class and CL-class cars.

“This is a classic case of lighting engineering moving faster than federal standards,” said Rae Tyson, a spokesperson for the NHTSA.

“We are seeing lot of new lighting innovations; some of them are allowed and some not,” Tyson added. “My understanding is [Mercedes] made a good case of allowing these brake lights to be used on a trial basis. Presumably they argued that flashing lights are just as visible, or perhaps more visible than regular lights. Whether they really are better remains to be seen, but we have faith in Mercedes engineering.”

Tyson points to a 1986 NHTSA law change that mandated that all new passenger cars include a center high mounted stop lamp, or “CHMSL” — a third stop lamp, or brake light, mounted on the rear of a vehicle. “We saw a safety benefit — a decline in crashes,” he said. “Anything you can do to raise visibility of a vehicle is good.”

One of the main reasons why car companies are experimenting with new lighting on their vehicles is the growing use of LEDs, or light emitting diodes.

Carmakers are using clusters of them to do the job of conventional incandescent bulbs in headlights, tail lamps and rear-window brake lights. The benefits are plentiful, experts say: LEDs are brighter than regular light bulbs, quicker to illuminate and more last longer. They’re developing other lighting systems to reduce traffic accidents, including Ford’s Adaptive Front Lighting, which steers lighting around corners and allows nighttime drivers to see better around curves.

“There is a movement toward LEDs in tail lights,” said Tom Appel, an editor with Consumer Guide Automotive. “You’re seeing them in luxury vehicles like the Infiniti M35, some Cadillac models and also in the Volkswagen Passat. They are much brighter, clearer and the length of time it takes to illuminate then is almost instantaneous.”

The idea that a flashing stop lamp could signal a vehicle’s rapid deceleration, and so prevent a rear-end accident, has been under consideration by auto safety and auto lighting experts for decades, notes Michael Flannagan, a research associate professor at the University of Michigan’s Transportation Research Institute.

“What Mercedes is proposing is not a wild and crazy idea; it’s right in the mainstream of what people in this field have proposed over the years,” Flannagan said. People who study driver vision have realized that humans are not very good at judging the closing rate on an object ahead of them, he added. “So it makes sense to add more stimuli — in this case a stronger stop lamp that responds to strong braking. It seems like it should be a good idea to supplement a natural weakness in human perception.”

The problems of traffic accidents in general are very complex and have many causes and solutions, Flannagan added. There are a finite amount of signals drivers can be expected to respond to, he said, but any modification that can add even a fraction of a second to a driver’s reaction time and potentially reduce the 40,000 fatalities on U.S. roads from automobile accidents each year, which cost the economy some $230 billion a year, or about $820 per person according to the NHTSA, is important.

“The economic and human cost is so enormous so every improvement is important,” Flannagan said, but added that it remains to see if flashing brake lights will do much to reduce road accidents.

“There is little evidence to suggest that this will help reduce accidents; that doesn’t mean it won’t, it just means it’s hard to gather supporting evidence,” Flannagan said. “Drivers respond to many other things in the road and good, attentive drivers are always looking a step or two ahead of the car ahead of them, so stop lights are not the whole story.”

Mercedes brake lights are already flashing in Europe; they are a standard feature in the new Mercedes S-class, which was launched there last September. They’re activated at speeds of 50 kilometers per hour (just over 30 miles per hour), or higher when a car brakes suddenly, or when the car is traveling on a low-friction surface like ice, snow or rain. Mercedes will introduce flashing brake lights to the United States when their flagship S600 goes on sale here in April 2006. The S65, due for release in July, will also include flashing lights.

In European testing, Mercedes found that drivers reacting to flashing brake lights hit the brakes in 0.4 seconds, slightly faster than the 0.6 seconds it took them to react to a regular brake light.

“We feel strongly that this adds a benefit to drivers,” said Robert Moran, manager of product public relations at Mercedes-Benz USA. “The S-class Mercedes has usually been the first of our cars to show our safety innovations, such as anti-lock brakes, or stability control,” he added, noting that safety features often start in the S-class and trickle down to our other models, so it’s quite possible flashing brake lights will soon trickle down to other cars in the Mercedes fleet.

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