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Why Are Semi Trucks So Slow? (11 Facts For Beginners)

Semi trucks are the giants of the motorway. Sometimes they can get in the way and hold up other traffic, which may be frustrating for motorists.

Have you ever wondered why semi trucks are so slow and why they struggle so much when going uphill? 

Read on to find out precisely what makes semi trucks so slow.

Here’s a quick answer to Why Semi Trucks are so Slow:

Semi trucks are slow primarily due to their size and weight. Often semi trucks will also be electronically limited to a specific speed limit. Semi trucks are also not aerodynamic. This means that they disrupt the airflow more than an average car which results in drag, therefore making them slower.

Why are Semi Trucks so Slow?

Semi trucks are slow mainly because of their size. The larger the vehicle is the slower it will be because of all the extra weight that needs to be carried.

Semi truck engines are often extremely powerful, however, this is mainly to create enough torque and pulling power for when the semi truck is hauling cargo.

When semi trucks have trailers connected to the tractor, they will often weigh significantly more than your average car, which can make them even slower.

Semi trucks are also sluggish when they are hauling cargo to ensure that the cargo remains safe and will not be damaged during transport.

Most semi trucks will also have their speed governed. This means that an electronic limiter is put on the truck, preventing it from going over a specific speed limit.

In some cases, drivers of semi trucks will also be driving slower than usual to save fuel. The less power the engine is generating the less fuel will be used.

Another critical factor that affects the top speed of a semi truck is the aerodynamics.

In most cases, semi trucks have poor aerodynamics, which slows them down significantly compared to the average car that is designed to be more aerodynamic.

Why are Semi Trucks Slow to Take Off?

Semi trucks are often the slowest vehicle to pull away from a standstill. There are several reasons for them being so slow when they take off.

Semi trucks are extremely heavy, and it takes a lot of power and traction to put everything into motion. This is especially true if they are carrying heavy cargo in their trailers.

Semi trucks are large, which is why they are so heavy and slow. Their size is what adds to their weight, and sluggish get away from a standstill.

Often semi trucks are also carrying fragile cargo.

This means that drivers need to be extra careful when they pull away from a standstill to prevent any sudden motion and momentum from causing any damage to their cargo.

The average time for a semi truck to go from 0-60 miles per hour in 20 seconds. On the other hand, the average time for a car to reach 60 miles per hour in 6 seconds.

With a heavily loaded trailer and a lot of cargo, a semi truck could take up a full minute to reach 60 miles per hour.

Why are Semi Trucks Slow to Stop?

Semi trucks take a much longer distance to stop than your average car. This is because they carry much more weight and, therefore more momentum than an average car.

Despite having stronger brakes, semi trucks still need that extra distance to slow down to a stop.

The average semi truck that is fully loaded with cargo can take up to two football fields to slow down to a stop. You should never cut in front of a semi truck and slow down.

In bad weather, slippery roads, or on roads that are in poor condition, this distance can increase dramatically.

For example, in heavy rain, the stopping distance of a semi truck can be double what it would be on dry tarmac.

Why are Semi Trucks Slow to Turn?

Semi trucks naturally have a large turning circle. This means that they need a lot of space to turn, and their turning radius is large.

In order to maneuver the semi truck accurately and effectively, drivers need to turn their trucks slowly.

Slower forward movements will reduce the turning radius of the semi truck and help them to make the corners much more comfortably.

Semi trucks also need to go around faster corners more carefully due to the amount of weight they have.

Going slower around these bends will prevent the weight from shifting around and causing the semi truck to tip over or cause an accident.

Semi trucks also need to take turns more slowly to prevent their cargo from being damaged. If the cargo moves around too much or too quickly, it can become damaged or even dislodged.

Why do Semi Trucks Drive so Slow on the Road?

Semi trucks have to follow the speed limits and drive slower than other cars because of their size and weight. If they drive too fast, it becomes a safety risk.

Most semi trucks are also governed, which means their speed is electronically limited. In some cases, companies can limit the speed of the semi truck to below the road speed limit.

Semi truck drivers are amongst the most responsible drivers on the road, and they follow tons of rules and regulations to ensure that their semi truck, cargo, and the motorists around them are safe at all times.

In poor weather conditions such as rain and heavy wind, semi trucks will drive even slower. This is because the bad weather severely hampers their stopping distances and stability.

Why are Semi Trucks so Slow when Driving Uphill?

Semi trucks are extremely slow when driving uphill because they are so heavy. Despite having incredibly powerful engines, a semi truck will still struggle to get up a steep incline.

In most cases, they also need to head into the incline with a lot of speed and momentum to try and get up the hill quicker and with less effort.

It’s a similar scenario as a small car with a less powerful engine. Despite the car being light and small, the engine might not be strong enough to get it up the hill.

Why are Semi Trucks so Slow when Driving Downhill?

Semi trucks are slow going downhill, mainly for safety reasons.

They have a tremendous amount of weight that pushes them from behind, and if their speed is not controlled going downhill, they can lose control.

With the weight naturally increasing the speed of a semi truck going downhill, a driver needs to be in full control by slowing the semi truck down.

A semi truck can also take much longer to slow down to a stop than your average car. This stopping distance is exaggerated when the semi truck has extra momentum while going downhill.

Why do Semi Trucks Overtake each other so Slowly?

Semi trucks often overtake one another if one is slower than the other. This might help the overtaking truck to keep up with their schedule and arrival times.

However, semi trucks are not fast, which means that overtaking is slow and can take much longer than expected. 

In most cases, when a semi truck is overtaking it can only go 2-5 miles per hour faster than the other truck.

This is only a small speed advantage which means it still takes several seconds for a semi truck to pass another one safely.

Are Semi Trucks allowed to Drive in the Fast Lane?

In many states, semi trucks are not allowed to drive in the fast lane as it poses a safety risk to other motorists on the road.

Semi trucks are only allowed to drive in the fast lane when overtaking another vehicle, exiting to the left, or making a left-hand turn.

If semi trucks drive in the fast lane, it could cause traffic to become backed up or even lead to severe accidents on the road.

Why do Semi Trucks have Low Top Speed?

Semi trucks have a low top speed for several different reasons.

These reasons come down to the way a semi truck has been built. It is important to remember that a semi truck is not built for speed but effectively transport cargo.

The weight of semi trucks makes them slower. The heavier a vehicle is, the lower its top speed will be. If a heavy vehicle were to go faster, it would need to have a more powerful engine.

Another reason why semi trucks have such a low top speed is because they have poor aerodynamics. Aerodynamics influences how the air flows around a vehicle.

With the square shape of a semi truck, its airflow is not smooth but more turbulent and disruptive, which causes more drag. Drag is what slows a vehicle down and lowers its top speed.

Any Regulations on How Fast or Slow a Semi Truck can Go?

Each state has a different speed limit for semi trucks. For example, in California, the speed limit for semi trucks is 55 miles per hour. Whereas in Arizona, it is 75 miles per hour.

These inconsistent speed limits in each state can become confusing, and it’s a good idea to double-check the speed limit of each state before going there.

In addition, some companies also govern their semi trucks to ensure that the driver can not go over the speed limit.

Governing a semi truck is a form of electronic speed limiting. The limit can be set beforehand, and the semi truck will not go faster than the set speed.