Driving down the highway or stopped at a red light, you may have seen a sign on the back of a semi-truck stating, “If you can’t see my mirrors, I can’t see you.” These signs are more important than you might think; they warn drivers about a truck’s no-zone, an area of zero visibility around the truck. But what is a truck’s no-zone, and what does it mean for highway safety?

The No-Zone

The graphic above illustrates the no-zone of a standard American tractor-trailer. This is an area of zero visibility, meaning truckers cannot see anything in the yellow zones.

Front and Back

A trucker has no rearview mirror, and most don’t have backup cameras. That means they typically can’t see the first 30 feet behind their trailer. If a car following too closely attempts to pass the trucker, they’ll move from one part of the no-zone to another and the trucker may never see them.

The same is true for the front of the vehicle. While European trucks tend to have flat front ends, like a bus, American trucks tend to have a long hood, and the driver sits about 10 feet off the ground. That means truckers can’t see the first 20 feet in front of their vehicle, making it extremely dangerous to pass a truck and then merge directly in front of them.

Left and Right

The side-view mirrors are angled to see far behind the vehicle. That means truckers typically can’t see what’s directly beneath the driver-side window, even if cars alongside them can see their mirrors.

The passenger-side mirror is concave, like a bubble, and has an even larger no-zone. In most cases, a trucker cannot see anything in the two lanes to their immediate right. This makes passing trucks on the right especially dangerous as the trucker may have no idea someone is there until they attempt to merge.

Staying Safe

When driving around large trucks on the highway, the best thing you can do is give them a little extra space, about three car lengths, whenever passing or merging. The truck driver will appreciate your considerate driving and you’ll be much less likely to end up in a crash.