Quicker, smarter, safer

| July 03, 2007

Collision warning systems keep tabs on how far you are from the vehicle in front using radar, which passes through fog and smoke.

Time is one of the biggest factors when it comes to avoiding collisions. Under even minimally favorable road conditions, it might be all you need to keep safe, provided your vehicle is in working order.

So how fast is your reaction time? According to David Pierson, sales manager for the Vehicle Solutions Business Unit at Eaton Corp., racecar drivers may react to a dangerous situation in about half a second, but truck drivers typically take about 1.5 seconds.

Even if your reaction time is faster, you can still travel a long way in the blink of an eye – at 60 mph, 120 feet in 1.5 seconds.

That 1.5 seconds is plenty of time if a driver is rolling along with traffic and maintaining a good following distance. A collision warning system is designed to ensure that you always have at least that much time to react. They make up for the one thing that can defeat even the best driver – a momentary lack of awareness. As Pierson suggests, a driver might be pulling a sandwich out of a cooler, tuning the radio, or even doing his job by scanning the mirrors for trouble to the side or rear when something that spells disaster happens just ahead.

“Scanning the mirrors takes two seconds, and that means you travel 170 feet without looking at the road,” he says. That’s at 58 mph. You can multiply your speed in mph by 1.47 to get the distance you’re traveling in feet each second, in case you want to consider some other examples.

As Delphi Automotive’s Active Safety Start Center Manager Michael Ray says, “The system forces a distracted driver to pay attention to what’s in front of him.” Delphi describes its system as “a collision warning and headway alert.” It is actually composed of this and optional subsystems that include the forward collision warning/headway alert system, a lane-departure warning system, and a blind spot warning system, all of which are integrated, connected to the same controller, which reduces the cost.

Collision warning systems typically offer visual and audible messages so you don’t have to be looking at them to become alerted. This lets them help you without compromising your view of the road.

Amazing smarts
One of the most impressive aspects of these systems is the intelligence they add to basic radar, enabling them to fulfill one of the largest requirements the engineers design into them: the avoidance of nuisance warnings. Pierson says Eaton’s radar operates at a frequency that’s 60 MHz (mega-hertz) away from police radar. This way, the system won’t become confused and give you a false warning when Smokey is taking pictures of you.

Both systems combine a radar unit, a processor and a driver display. Their intelligence also allows them to be particularly smart about catching every dangerous situation. They incorporate not just radar receivers but also speed sensors and microprocessors, which are normally mounted, as in the case of the system made by Delphi Automotive, separately from the radar unit, well inside the cab.

Why is avoiding useless warnings so important? For the same reason the DOT should remove construction zone signs consistently once the work has stopped: People ignore inaccurate sources of information even when they know the source may sometimes be correct. As you might imagine, engineers have found that drivers will react negatively to a system that constantly bothers them when they are driving safely. In fact, they won’t just fail to pay attention to it, they will turn it off or, if that’s not possible, deliberately disable it.

By having enough of the right information and making sense of it, these systems manage to warn you only under critical conditions. They measure the distance of the vehicle ahead at frequent intervals. They also incorporate knowledge of the passage of time and some math. They combine those with an mph input from the vehicle’s speed sensor.

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