Here’s something you may not realize: Your car may have rear fog lights. Not all cars do. Some cars only have front fog lights. Some cars have no fog lights at all. But some cars have front and rear fog lights — and you should really never turn on your rear fog light unless you’re driving in heavy fog.
First, let’s discuss why the rear fog light exists. It’s mandatory in Europe, and it’s a bright red light — precisely as bright as your brake lights — that reveals the position of your vehicle. This is so your car can be seen in dense fog; normal (fairly dim) taillights couldn’t be spotted in such conditions, so the rear fog light is designed to be brighter and to make your car more visible.
For many years (and still today, in some cars) the rear fog light was placed on the left side of each vehicle. There was a reason behind this, too: If you’re trying to pass in dense fog, you don’t just want to know a vehicle is present, you want to know generally where it’s located in the lane and on the road. With a rear fog light always located on one side, you always have a good idea of the position of the car you’re passing. In many modern cars, the rear fog light is on both sides, which serves roughly the same purpose.
So why shouldn’t you drive around with the rear fog light on unless you’re in heavy fog? It’s simple, really: The rear fog light is placed in the vicinity of your brake light, and it’s about the same brightness as your brake light — meaning that if you’re driving with the rear fog light on, it can be easily confused with your brake light. Cars behind you won’t have a good idea of when you’re actually stopping and when you’re just letting them know your position in dense fog that doesn’t exist.
With that said, this is one of the few driving mistakes I don’t blame on the individual. Most people have no idea the rear fog light exists or that their vehicle has one. More importantly, most people have no idea they’ve accidentally turned on their rear fog light, as it can easily be inadvertently tripped: It’s the button with a graphic of a light pointing to the right, and fog to the right of the light. Only a small warning light usually shows up in your gauge cluster to let you know it’s on.
But, indeed, it is on, and it’s making it harder for other drivers to see that you’ve stopped — so be sure to make sure you’ve turned off your rear fog light unless you’re driving in dense fog.
Doug DeMuro is an automotive journalist who has written for many online and magazine publications. He once owned a Nissan Cube and a Ferrari 360 Modena. At the same time.