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1.15 Size Limitations

Drivers must obey all posted signs regarding maximum truck width, length, height and weight limits. They must be aware that some highways prohibit truck travel entirely. Others allow truck travel on a limited basis.

For example, only very small trucks may cross certain township bridges as well as the highways leading to and from these bridges. Higher limits are allowed on state highways designated by individual states and on local streets and highways designated by local government officials.

These heavier and larger vehicles and combinations are allowed to travel on non-designated streets or highways in the state highway system for up to five miles to gain access to a designated roadway. These vehicles are prohibited on all streets and highways under local jurisdiction unless designated by local officials.

Width

The maximum width for most vehicles traveling on the United States Interstate System is 8 feet, 6 inches. While some individual states may have their own maximum limits on US Interstates within their state boarders, those limits must meet or exceed 8 feet, 6 inches .

Length

No vehicle with or without a load, other than a semitrailer, shall exceed a length of 42 feet. Semitrailers may have an overall length of 53 feet, including the load being carried. However, for semitrailers more than 48 feet in length, the maximum allowable distance from the king pin to the rear axle can vary by state.

Exceptions to these limitations are vehicles hauling pipes, poles, machinery or other structural objects that cannot be quickly taken apart. In most states, the length of these objects may not exceed 80 feet, except for public utility emergency repairs or for those holding special permits. These vehicles are not allowed to operate when it is dark or on Saturdays, Sundays and legal holidays.

Height

The maximum height for all vehicles on all designated state and federal highways is 13 feet, 6 inches, including load from the underside of the tire to the top of the vehicle. This includes the US Interstate system. Individual states may set their own maximum height limits, but those limits must be equal to or greater than 13 feet, 6 inches.

Weight

The maximum weight limits on both designated and non-designated streets and highways are:

  • 20,000 pounds on a single axle.
  • 34,000 pounds on a tandem , and
  • Up to 80,000 pounds of total weight on a 5-axle combination, depending upon axle spacing.
The only thing you'll need to memorize for maximum width is 8ft 6in. But if you're curious to learn about your state specific limits on local and state highways, you can download a copy of your states CDL manual for free.
The most important number to memorize in this paragraph is the maximum allowable trailer length of 53ft. State specific info concerning the distance from kingpin to rear-axle is not likely to show up on your exam.
Very important! It is extremely likely you will receive a question on the written exam regarding maximum allowable vehicle height. Be certain to memorize 13ft 6in as the maximum height allowed. A few states do have their own limits (usually 14ft or 14ft 6in) but all states MUST abide by the federal minimum of accepting vehicles that are at least 13ft 6in on designated Federal and State Highways.
It's crucial that you understand and memorize the below vehicle weight limits, especially the weight limits per tandem and total weight. Be sure you understand the difference between an axle and a tandem (tandem = pair of axles such as the rear wheels on a truck trailer).
The only thing you really need to remember here is that oversize vehicles (which includes over length vehicles) may not operate when it is dark, which is generally accepted as sundown to sunrise.
While nearly all states have a single axle limit of 20,000 pounds, a few states do vary. The lowest single axle weight limit in the country is 12,000 pounds. Questions about single axle weights are very unlikely to show up on your written exam.

CDL:

Commercial Driver's License (CDL)

A CDL is required to drive any of the following vehicles:

  • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
  • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
  • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
  • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Interstate:

Commercial trade, business, movement of goods or money, or transportation from one state to another, regulated by the Federal Department Of Transportation (DOT).

HOS:

Hours Of Service

HOS refers to the logbook hours of service regulations.

Review Questions - Click On The Picture To Begin...

The maximum allowable width for commercial vehicles on designated state highways is:
  • 9 feet
  • 8 feet
  • None of these answers are correct
  • 7 feet 6 inches

Quote From The CDL Manual:

Width

The maximum width for most vehicles traveling on the United States Interstate System is 8 feet, 6 inches. While some individual states may have their own maximum limits on US Interstates within their state boarders, those limits must meet or exceed 8 feet, 6 inches

Next
What is the maximum trailer length allowed?
  • 60 feet
  • 53 feet
  • 48 feet
  • 50 feet

Quote From The CDL Manual:

Length

No vehicle with or without a load, other than a semitrailer, shall exceed a length of 42 feet. Semitrailers may have an overall length of 53 feet, including the load being carried.

Prev
Next
What is the maximum weight limit for a 5-axle combination vehicle?
  • 20,000 pounds
  • 100,000 pounds
  • 34,000 pounds
  • 80,000 pounds

Quote From The CDL Manual:

Weight

The maximum weight limits on both designated and non-designated streets and highways are:

  • 20,000 pounds on a single axle.
  • 34,000 pounds on a tandem, and
  • Up to 80,000 pounds of total weight on a 5-axle combination, depending upon axle spacing.
  • 20,000 pounds on a single axle
  • 34,000 pounds on a tandem
  • 80,000 pounds on a 5-axle combination, depending upon axle spacings.

TruckingTruth's Advice:

A "tandem" is a reference for a pair of axles. For example, the rear 2 axles on a tractor and the rear two axles on the trailer are considered tandems. So a single axle (such as the front axle) can have a maximum of 20,000 pounds. A tandem (two axles in close proximity) may have 34,000 pounds. But the entire weight of the vehicle can not exceed 80,000 pounds.

Prev
Next
What is the maximum allowed vehicle width on designated US Interstates?
  • 10 feet
  • 8 feet, 9 inches
  • 8 feet, 6 inches
  • 13 feet, 6 inches

Quote From The CDL Manual:

Width

The maximum width for most vehicles traveling on the United States Interstate System is 8 feet, 6 inches. While some individual states may have their own maximum limits on US Interstates within their state boarders, those limits must meet or exceed 8 feet, 6 inches

Prev
Next
What is the maximum height for all vehicles on all highways?
  • 13 feet, 6 inches
  • 13 feet
  • 14 feet, 6 inches
  • 12 feet, 9 inches

Quote From The CDL Manual:

Height

The maximum height for all vehicles on all designated state and federal highways is 13 feet, 6 inches, including load from the underside of the tire to the top of the vehicle. This includes the US Interstate system. Individual states may set their own maximum height limits, but those limits must be equal to or greater than 13 feet, 6 inches.

TruckingTruth's Advice:

Any vehicles exceeding 13 feet, 6 inches in height must obtain proper permits.

Prev
Next
What is the maximum allowable weight on a tandem axle?
  • 40,000 pounds
  • 80,000 pounds
  • 20,000 pounds
  • 34,000 pounds

Quote From The CDL Manual:

Weight

The maximum weight limits on both designated and non-designated streets and highways are:

  • 20,000 pounds on a single axle.
  • 34,000 pounds on a tandem, and
  • Up to 80,000 pounds of total weight on a 5-axle combination, depending upon axle spacing.
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