What Is Perimeter Lighting on a Car?

One of the stock features of a thriller -- in the movies or on television -- is when someone enters their car only to find it occupied by an unexpected person who greets them with a gun, a knife, a threat or a plea. It's usually at night, meaning the person hiding in the car is cloaked in darkness. Perimeter lights play on this real possibility and the paranoia of the movie-going, television-watching public. Even though many of these people may have never heard of perimeter lighting, and even though few of them will ever have a similar experience, the only people who might be disturbed by perimeter lighting's presence are the people who would hide in an unlit car in a darkened parking lot.

While it's unclear what automobile manufacturer introduced perimeter lighting first, remote keyless entry and starting systems appeared in American production cars in the early 1980s. General Motors made these systems available in its 1989 vehicles. The keyless entry system, which relies on a very-short-range radio transmitter, is available on most mid- to upper-price range vehicles. Technology required to unlock the door using a simple electromagnet was easily expanded to activate the interior lights as if the door had opened.

Because the automotive world is driven by consumers' perceptions of comfort and security, even the least expensive offerings from Ford and Chevrolet offer a perimeter security system, including perimeter lighting, available either as a standard feature or as an option. At the least, vehicles that have neither a security system nor perimeter lighting have an "illuminated entry" system that turns on the interior lights when a door is open or left ajar.

Going back to the image of the strangler in the back seat, the security advantages of perimeter lighting over illuminated entry are several. With illuminated entry, you must open the car door before the lights come on. By that time, you've probably got one foot in the door and are sliding into the driver's seat, ready to offer your neck to the mugger in the back seat. With perimeter lighting, you can push a button as you walk toward your car. When the lights come on in the interior well before you get to the car, the murderer lurking in your back seat loses any advantage because you have the opportunity to inspect the interior before you even open the door and the perimeter lighting system has done its job.