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So you were driving down the interstate the other day and noticed something odd: a semi truck with a tiny window at the bottom of its passenger-side door. No, it’s not for truck drivers with a little pet dog who wants to see what’s going on. It’s a way to reduce one of a semi truck’s biggest blind spots. You might be shocked how difficult it is for truck drivers to see your car next to them.

Some drivers refer to semi truck’s blindspots as “no zones” because it is a bad idea to stay in them for long. There is a blindspot on each side of a semi truck. The smallest is next to the driver’s side of the truck. But it is much bigger than the blindspot on the driver’s side of your car, partly because a semi truck pulling a trailer has no center rearview mirror.

The longest blindspot near a semi truck is directly behind its rear bumper. A truck driver may not be able to see any cars in its lane for up to 200 feet behind their rear bumper. If you can’t see the driver in one of the mirrors, the driver can’t see you. This is an especially dangerous zone because if you rear-end a semi truck, your car may slide beneath it.

The righthand-side blindspot next to a semi truck and trailer.
Semi truck and trailer | ziggy1 via iStockPhoto

Many motorists don’t realize that a semi truck’s hood blocks the driver’s view directly in front of the truck, for 20 feet. Yup, you could park a full-size car directly in front of a semi truck and it would be invisible to the driver. When passing a semi truck, it is a good idea to drive far enough ahead of the truck that you can see the entire vehicle in your own rearview mirror before signaling and pulling into its lane.

The widest blind zone near a semi truck is on the passenger’s side. A semi truck driver may not be able to see anything next to or behind their cab for three lanes on their right. It is very dangerous to pass semi trucks on the right. Some semi truck manufacturers have tried to address this problem by installing a fish-eye mirror on the righthand side fender of the truck. Others have even added a window low in the passenger-side door so the driver can see passing cars and/or see an additional mirror. In certain instances, this may increase the driver’s visibility. But there is still no guarantee they will see cars on their righthand side, so this blindspot is the most dangerous “no zone.”

Next, learn why some semi truck trailers have a tiny door set into their main doors, or see the Truck Smart YouTube channel illustrate just how large semi truck blindspots can be in the video below:

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Staff Writer

Henry Cesari

Henry Cesari joined MotorBiscuit in 2021 and brings his deep interest in vintage cars, trucks, and motorcycles to the site. Having restored his first classic car at just 16 years old, Henry has wrenched on everything from overland campers to Japanese motorcycles and even pre-war Bugattis. Henry is also an avid attendee at local car shows and genuinely enjoys connecting with fellow auto enthusiasts.

Henry earned a Bachelor’s in Anthropology and English from the University of Vermont. He has since incorporated his love of the written word with his admiration of classic cars. While Henry is interested in vintage cars, he believes the golden age of cars is yet to come. He is confident journalists will play an important role in this revolution by exposing the industry as it is now and envisioning its possible future.