A Semi truck has a very wide turn radius, with the radius increasing based upon the length of the trailer.
The trailers can range from a 30 footer to an oversize trailer, and each has a turning radius that differs drastically.
Here’s a quick answer to which Semi Truck has the Best Turning Radius:
The Volvo VNR semi truck models are designed to have a good turning radius, which helps navigate tighter turns with more precision and ease. The VNR 300 is the best truck for small spaces and residential roads. The distance between a truck’s axles is most important for turning radius capabilities.
What is the Turning Radius in a Semi Truck?
The turning radius in a semi truck is the amount of space required for a semi truck to make a certain degree turn. This is most commonly determined by finding the size of the truck by knowing the wheelbase of the truck.
Two of the most common sized semi trucks are the Wheelbase (abbreviated to WB) 40’ or 50’. This refers to the distance between the front and back tires, and helps to determine how much space will be needed to make the turn.
On average, semi trucks of this size need double the space to make a 90 degree turn (a relatively smooth right turn at a traffic light).
Although, for a 180 degree turn, they may need up to 3 times the amount of a regular car. To help illustrate this fact, while a car turns comfortably in lanes of 10 ft. width, semi trucks require lanes of 12 ft or more.
There are other sizes as well, such as WB70 which is the type you’re likely to see with “oversize load” signs posted on it. This type will need far more turning space than the ones mentioned above, but we will focus primarily on the WB40s and 50s.
How does Turning Radius affect a Truck Driver’s work?
The truck driver needs to take their surroundings far more seriously than a small passenger vehicle. Keep in mind that the average semi truck has 40-50 feet between front and back wheels, the average car has 23 feet or less.
How this translates when you drive is to be extra cautious and hope the back of the vehicle follows your path trajectory.
If you are in a small sedan and make a steep right turn you are often more concerned about hitting the neighboring car with the front of your car. You don’t think much of the back.
In a semi truck the wheelbase has a huge impact on every turn. When a semi truck makes a 90 degree turn, the back wheels are often pivoted differently from the front.
Therefore, when you make this turn you need to ensure the back trailer does not swing out so far that you hit the cars on the opposite side.
Check this video below that demonstrates this factor really well:
What is a good Turning Radius for a Semi Truck?
It takes a little trigonometry to figure out the turn radius of your truck and whether it will handle certain turns well.
First, you’ll need to figure out the wheelbase, which, as we’ve discussed, is usually the space between the front and back tires.
For certain types of trucks with tandem axles, measure from the axle to the back tires. You can also check the owner’s manual if you are unsure. Convert this to inches and calculate it on a scientific calculator to get your radius which is then converted back to feet.
You can find further details on this math equation and how it can be helpful to determine your turns at the following link: https://nacto.org/docs/usdg/truck_safety_considerations_for_geometric_design_and_traffic_operations_donnell.pdf
To simplify this a little, when determining what is a good turning radius, first figure out how steep the turn is. Obviously, it is useful to check your route on google prior to leaving to see if any turns may prove difficult to make.
Last, when making steep right turns, utilize any open lanes which may be at your disposal with caution and turn slowly and when the coast is clear.
Which Semi Trucks have the Best Turning Radius?
First, we will discuss the Peterbilt since there is some disagreement about this truck company’s capabilities in town. This brand is infamous for its hauling capabilities but the size and axle design makes it difficult to handle in town.
One model which has some disagreement, however, is the Peterbilt 359. This model is a large truck with great hauling capacities, but it has a longer axle for handling turns with more precision and ease.
Still, the size and weight of this model can cause it to have difficulties, especially on one-lane roads.
The Volvo VNR series is designed especially for city and suburban driving. The VNR models have been modified to navigate tighter turns with more precision and ease and to prevent the back from flying out too much.
There are 3 popular models in this series, from the VNR 300, 400, and 640. The VNR 300 is the smaller model which is best for small spaces and residential roads.
The VNR 640 has good space for sleeping and living and is better for potentially longer routes which will take you through towns and cities.
What affects Turning Radius in a Semi Truck?
The thing which impacts the radius in a semi truck the most is the wheelbase distance and the type of axle you have on your truck.
Some truck axles are better designed for handling steep turns without swinging out into oncoming traffic too much.
Street design has a strong impact on the turning radius of a semi truck as well. Some corners at intersections cut very tight, with edges which are triangular rather than rounded.
This can make steep turns very difficult, but fortunately many state county routes and highways are working to improve this fact.
Last, the other major factor regarding turn radius is that the weight of a semi truck can have profound impacts on the local road pavement.
And, vice versa, the truck can experience much wear and tear from the poorly tarred roads, which can make navigation complicated.
This is not directly connected to maneuvering, but it is important when navigating in order to protect yourself and your truck from unnecessary wear.
More details can be read on 6A-2 document from the Iowa Department of Transportation Office of Design.
Does the Length of your Trailer affect the Turning Radius of a Semi Truck?
The short answer is, it definitely does impact your truck’s maneuvering and turn radius. The most difficult part of driving the truck is the potential right-hand or left-hand turn you may need to take.
Highway driving is not strongly impacted by the size of your trailer unless the weight is excessive, or the torque of your truck is insufficient to haul the load up hills.
As far as highways are concerned though, navigation is primarily straight with slight curves rather than steep bends, so the trailer isn’t very impactful on the driving experience.
Inner-city driving, a trailer over 32 feet can prove very difficult to steer and park effectively.
This is because the trailer swings very wide, and with so much traffic clustered close together it is hard to make steep turns and bends.
Does the Type of Trailer affect the Turning Radius of a Semi Truck?
The simple answer is, the type of trailer can have a huge impact on your ability to turn and navigate well.
There are a lot of different varieties of trailers for your truck, and each is preferred for a different reason.
For simplicity we’re only going to look at 3 types which have aspects ideal for city/town driving.
The first is the extendable trailer. This may seem obvious, but this trailer is great for city driving because of its versatility.
It is a smaller trailer which can be extended when needed, but can also remain smaller than most semi truck trailers you’ll see on the highways.
The final two which are common for city driving but may be more difficult due to their potential weight are the dry trailers and refrigerated trailers.
These are common because of the cargo they carry, which is usually dry goods or perishable goods for grocery stores.
The simplest solution is to be wary of the length of your trailer and how heavy your load is when selecting a route.
Can the Turning Radius in a Semi Truck be Improved?
The best way to stay safe while turning your tractor trailer is to be aware of your surroundings.
Check your mirrors often, and be sure to signal long before your turn to ensure everyone around you is prepared and aware of the movement.
Also, to get better maneuverability with your trailer, try to shift the tandem so the weight of the load is off of your truck’s driving axle. When driving in the city, this can make it easier to turn safely and smoothly.
Be sure to follow all local and state laws when traveling and ensure the load doesn’t surpass requirements. This can help ensure your safety and efficiency when traveling on city roads.
Tips on Turning and Maneuvering your Semi Truck
First and foremost, plan your route ahead of time, and scout out difficult turns and intersections.
Remember that traffic has a huge influence on your ability to turn well so if it is possible, try to be in difficult places when there is likely to be less traffic.
You can oftentimes check on google maps for high traffic volumes for certain locations, to see local reports on the traffic volumes. Remember to use the road to your advantage as long it is safe and clear of traffic.
Safe turning is a group effort, and if you notice some cars are further into the intersection than they should be, do not try to push your luck. Wait until the next clear chance and make your move.
This document on wide turns from Truck Smart helps to illustrate how the lack of cooperation on the roadways can affect everyone’s safety.