General Motors has made some questionable decisions in the past. In the past decade or so, they gave us a mid-sized SUV with a retractable roof, a convertible retro-styled pickup truck, and a turbocharged sedan delivery. Now, though, these wacky side projects have been discontinued, and GM is back to making relatively justifiable decisions. Mostly.

All vehicles have lights on their posterior body panels. When reverse gear is engaged, some of those lights — specifically, the white ones — illuminate, so people behind the vehicle know it is about to travel in reverse. This has been the case for decades. Therefore, white lights at the rear of a vehicle are universally understood to indicate imminent travel in the reverse direction.

At some point, General Motors decided these reverse lights should also mean something else, so they now illuminate when the car has recently been unlocked. This, of course, can lead to confusion — most drivers in a parking lot who encounter a vehicle with its reverse lights illuminated will assume that vehicle is about to reverse. If it’s a GM car, how do you know? Do you wait there like an imbecile, irritating the motorists behind you?

In fact, there is a simple way to know whether a GM car with illuminated reverse lights is actually in reverse gear.

How do you tell?

Most GM vehicles — the Tahoe, Silverado, Traverse, etc. — are only available with an automatic transmission. If an automatic car is stationary and in gear, it will move. To prevent this from happening, drivers will apply the brakes. Most drivers will want to do this when backing out of a parking spot so they can survey their surroundings and ensure it is safe to proceed. When this happens, the brake lights will illuminate. This means, if a stationary GM car is actually in reverse, its brake lights will be illuminated.

So there you have it. To determine whether a GM car is in reverse, look at the brake lights. Of course, this would not be necessary if GM were a normal car company, but they aren’t. Now, perhaps, your parking endeavors can be marginally less stressful.