Semi trucks are some of the most recognizable vehicles on the road. Massive, 53-foot trailers pulled by sloping cabs deliver our food, drinks, gas, and Amazon packages all over the country. Because of their important functionality, it’s no surprise that there are strict rules in place about how big they can be.
The length of 53 feet for semi trailers was originally determined by their cargo type and by limits on the overall categorization of the vehicle. As shipping methods evolved and changed, so too did the size and construction of shipping vehicles at the federal level.
Read on to learn how the federal government decided on the minimum length of semi trailers, and the exceptions to those rules.
Where the 53-feet Benchmark Came From
While most people will consider the weight of a semi truck in its restrictions, there are actually federal regulations on nearly all aspects of a semi truck’s construction. These rules categorize them based on axle number, unit load, and freight type, as well as length and weight. The Federal Highway Administration (FHWA) defines nine types of semi trucks that can be split into three general categories.
- Single-unit trucks have permanently attached trailers. These are usually vehicles like beverage delivery, mail carrier vehicles, cement mixers, and trash trucks.
- Longer Combination Vehicles (LCVs) are trailer-truck combos that weigh over 80,000 pounds and can carry three or more trailers.
- Combination trucks are the most common type, also called 18-wheelers. They’re five-axle commercial trucks with a detachable cab and trailer combo.
Combination trucks are the category for whom the 53-foot benchmark applies.
How the Length of Semi Trailer Became 53 Feet
In 1982, the United States government passed a series of laws known as the Surface Transportation Assistance Act. These laws dictated the regulations controlling the construction and operation of overland travel for commercial and federal use, including larger vehicles allowed to travel on interstate highways.
48 Feet Used to Be Enough
These laws included provisions about the size of the vehicles and prohibited trailers shorter than 48 feet in length. This size was chosen because of the standard size of shipping pallets, which were 48 inches long by 40 inches wide. A length of 48 feet was enough to fit roughly 12 pallets inside the trailer, which was roughly the amount of storage needed for a standard load of cargo without going over the weight limits in place and overstressing the vehicles.
Larger Loads Meant Longer Trailers
As construction became easier and better equipped to handle larger loads, the federal regulations changed to allow another pallet’s length in the trailers, bringing the standard up to 53 feet. Now, because of further improvements in semi truck construction, states can choose to allow vehicles with trailers up to 59 feet long on non-federal roads.
Federal Length Regulations on Semi Trailers
Oddly enough, the rules for semi truck trailer length can vary from state to state. Federally, the most important sizing mandate is that, on a five-axle semi truck that travels on the interstate and federally maintained access roads, the trailer can’t be less than 53 feet. That being said, many states allow smaller trailers on state-funded roads and longer trailers on all roads.
State Level Exceptions
As mentioned, the original legislation for semi truck trailers was that they couldn’t be shorter than 48 feet. In many places, these rules have been grandfathered in, though only for non-federal roads and access ways. The states that allow shorter trailers are:
- Alaska
- California
- Connecticut
- Idaho
- Maine
- Maryland
- New Hampshire
- New Jersey
- New York
- North Carolina
- Rhode Island
- Utah
- Wisconsin
All of these states allow for trailers between 48 and 49 feet in length (one of the common allowed lengths is 48.5 feet, for some reason) on designated secondary highways or non-designated truck and service highways. These trucks are generally used for small cargo loads traveling within the state or even simply within a few counties.
Conclusion
Semi trucks are something like the blood in a vascular system. They provide vital pieces of everyday life, transporting them from manufacturers to consumers to keep up with the demands of the country on a daily basis.
Without semi trucks, delivery of goods and raw materials would be significantly harder – in some cases; it would be impossible (such as with refrigerated delivery). This is why there are such strict legislative restrictions and provisions in place. The federal government needs to be sure that the transit of goods across the country isn’t interrupted.
