ByLawDrivingSchool Cutting off semi

Cutting Off A Semi

This post comes from the request of many truck drivers that I know. Hopefully it does them justice and gets the point across to all you new and seasoned drivers!  Thanks Ginette C!

Cutting off a Semi is a No No!  The hardest part of being a professional truck driver is  driving through rush hour traffic. A semi (as well as a school bus or big delivery truck) needs significantly more stopping space/time to safely come to a complete stop. According to an article on :

Stopping Distance-cutting off a semi decreases distance

It takes approximately 316 feet (96 meters) for a normal passenger car to come to a complete stop. A semi truck takes about 525 feet (160 meters) before it comes to a complete stop. To accurately calculate the stopping distance of the vehicle, different factors are taken into consideration.

Reaction Distance

The perception of an impending danger. The driver of a passenger vehicle usually takes 1.5 seconds to perceive a dangerous situation and apply the brakes. This time is about the same for the average truck driver.


Semi trucks have larger brakes than other vehicles, But it takes a semi truck much longer to stop because of the much larger weight of the semi truck. Cars have an average weight of 5,000 pounds (2268 kg) while a semi truck can weigh up to 80,000 pounds (36,287 kg). A car takes about 124 feet (37 meters) to come to a stop when traveling at 40 mph (65 km) per hour from the time that the driver perceives the danger. In comparison, a truck driver takes approximately 169 feet (52 meters) from the danger perception time when traveling at the same speed.


The faster a vehicle is traveling, the longer it will take to come to a complete stop. In comparison to the figures noted above, a passenger vehicle will take about 316 feet (96 meters) from the awareness point when traveling 65 mph (105 km). The semi truck takes about 525 feet (160 meters) before coming to a complete stop.

Other Variables

Weather can play a major part. When there is rain, snow or ice on the roadway, braking distance is increased significantly. Road conditions can also be an important variable in determining the anticipated stopping distance of a semi truck. Additionally, the tire treads and the manner in which the brakes are applied can affect the stopping distance of semi trucks. Factors that affect the driver’s ability to recognize a danger can also impact the calculation.

The Law

In closing I just want to bring to people’s attention the white lines on the roads. I’m sure you all have seen the white dotted lines while driving in the city. Those line mean its ok to change lanes. But did you ever notice how at any controlled intersection, those white dots merge together and become a solid line? That means you are not suppose to change lanes anymore!! There is a reason for this. You change lanes at this point and have to stop, you just cut the stopping distance for that person behind you and you have officially cut them off! Obey the law. Those markings are not just crayon lines that bored city workers decided to plop down on the streets. They all mean something. They are there for your safety!

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