If you spend a lot of time on the road, you will see countless 18 wheelers every day. Also known by several names like big rigs, semi-trucks, semis, tractor-trailers, semi-trailers, or semi-trailer trucks, these are vehicles that are made by combining a powered truck and trailers. These large trucks are used all over the country to take goods to and from each state.
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A typical 18 wheeler will have two or three axles, but those designed to pull heavy-duty commercial construction equipment may have up to five, with some being lift axles.
The most common 18 wheeler layouts include a forward engine, one steering axle, and two driving axles. The fifth-wheel trailer connections on most tractor vehicles are movable fore and aft to allow for weight distribution modifications over the rear axles.
Here are some fun facts about 18-wheelers.
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How Long Is an 18 Wheeler?How Long are 18 Wheelers?
An 18 wheeler is typically 70-80 feet long, combining the tractor and trailer.
Depending on some factors though, the length may vary significantly.
Sleeper cabs, which have a bed inside for truckers hauling further away from home, are typically roughly 20 feet long, though this can vary depending on the manufacturer and specification.
A typical dry van trailer is 53 feet long and measures around 70 feet when extending a few feet over the vehicle. Double or pup trailers are typically 28 feet long, whereas intermodal containers might be 20 or 40 feet long. Tanker trailers, flatbed trailers, and several other trailer types come in various lengths.
Companies can often get creative with the length of equipment for unique freight demands, but each state has its own limitations on overall length.
How Much Do They Weigh?
18 wheelers can have a gross vehicle weight of up to 80,000 pounds with both the tractor and trailer under most weight restrictions. This is normally shared between the steer axle and the drive and trailer tandem axles, with the steer axle weighing up to 12,000 pounds and the drive and trailer tandem axles weighing up to 34,000 pounds.
Oversized loads that exceed those restrictions require special permission.
The type of CDL (Commercial Driver’s License) a truck driver has also influences the amount of weight they may transport (e.g., Class A vs. Class B CDL).
How Tall are They?
The average 18 wheeler is 13’ 6” tall.
Why do 18-Wheelers Drive Slower than Other Vehicles?
Have you ever been stuck behind a slow-moving truck and wondered why they do lower than the speed limit? Many 18 wheelers have built-in speed limiters (also known as governors) to enhance fuel-efficiency, which is good for the environment. For example, Schneider’s speed stance for many tractors is 63 mph.
This is why, if one semi-truck travels at a speed of 2 mph faster than the other, two semi-trucks may pass each other for long periods.
In some states, trucks have their own set of speed limits. Going at a slower speed is also beneficial if the truck has to perform an emergency stop for some reason.
How Long Does it Take for Them to Stop?
The average time it takes an 18-wheeler to come to a complete stop is 40% longer than it takes a vehicle. So if a truck is traveling at 55mph and the driver applies the brakes, the vehicle will take the distance of 2 football pitches to completely stop.
These measurements are influenced by the weight of the truck’s load, whether it’s bobtailing, road conditions, weather conditions, and other things. Trucks only have ten brakes, not eighteen, and anti-lock brakes are now standard equipment on all new trucks.
What is Bobtailing?
A truck driver is considered to be “bobtailing” when he is not dragging a trailer. Driving just the cab section of a truck is referred to as this.
Ironically, because the trailer’s stabilizing weight is missing, bobtailing can be quite dangerous, especially in bad weather. It can also affect how well the driver can break and come to a complete stop.
How Many Miles Can They Go on One Tank of Gas?
With 300-gallon tanks and a 7-mile-per-gallon average fuel efficiency, 18 wheelers can travel roughly 2,100 miles on a tank of diesel fuel (not widely used gasoline).
Of course, each driver must be aware of the size and efficiency of his or her truck’s gasoline tank. Many companies offer fuel optimization solutions to assist drivers to make the most of their fuel breaks while staying safe, and Schneider is a pioneer in the area when it comes to fuel efficiency.
How Well Can They Drive Up and Down Hills?
There are ten forward and two backward gears on most modern trucks, though some trucks may have anything from 13 to 18 gears. Truck drivers also utilize a double-clutch shifting system to match the engine’s RPMs to the appropriate gear for that RPM range.
When traveling up or down an incline, a truck driver must select the appropriate gear based on the engine’s RPMs. This might cause a “slow” ascent and downshifting when leveling out after a hill.
What Happens if They Blow a Tire When Driving?
18 wheelers have two sets of tires, known as a tandem system. This is a backup in case one tire blows on the road. If this happens, the other tire will continue to hold the weight of the truck and keep the whole vehicle steady until the driver can stop safely and make repairs.
What’s a Jack-Knife Accident and How Does it Happen?
When a truck’s trailer is at a 45-degree angle from the cab, it’s more likely to cause a jack-knife accident. When a driver comes to a sudden stop on a wet or slick road, the vehicle may begin to skid and slide. A jack-knife will occur if the trailer starts to spin towards the trailer faster than the cab.
In addition to jack-knifing, tractor-trailer trucks are prone to all types of accidents because of their sheer size. In regards to a trucking company’s crash records, anyone can check the safety history of a trucking company through via the Safety and Fitness Electronic Records (SAFER) System.
An 18-wheeler’s 5th wheel is placed directly behind the cab. It’s a huge round metal plate that connects and secures the trailer to the truck above the driving tires.
How Much Does an 18 Wheeler Cost?
To the average person, semitrailers are highway behemoths that you wouldn’t want to find yourself driving next to. To kids, they are a source of awe and entertainment on long drives. To all of us though, commercial trailers are the arteries and veins that keep the country moving. They are the conduit through which your favorite cereal ends up on the supermarket shelf, your Amazon delivery reaches you on time, and gas is available at your local gas station.
There’s no question about it—semitrailers are imposing, not to mention oversized loads like those carried by schnable trailers. You may be familiar to some degree with weight restrictions, but less well known are trailer length restrictions. There are semitrailer length laws by state as well as at the federal level. Before we get into that, let’s take a quick look at the typical truck configurations in America.
There are many ways commercial trucks can be classified and defined. The FMCSA defines commercial trucks as road vehicles with a gross vehicle weight of more than 10,000 pounds designed to carry freight. The FHWA categorizes freight-carrying vehicles into nine classes based on the number of axles, the number of units, and the type of unit combinations. Nevertheless, most commercial truck configurations in America fall into three main categories.
More widely known as the 18-wheeler, the five-axle tractor semitrailer is the most recognizable commercial truck in the USA. The tractor (i.e. power unit) is either a sleeper cab or a day cab. Sleeper cabs have a sleeping berth or small living area in the tractor. They are typically used for long-haul operations. Day cabs have a shorter wheelbase and are used for short haul operations, such as delivery and pickup. The freight-carrying unit of a tractor semitrailer vehicle usually varies between 40 and 53 feet in length; although, some states allow semitrailer lengths of up to 59′ 6″.
A straight or single-unit truck is a commercial freight road vehicle where the vehicle chassis and power unit are permanently attached. Straight trucks are most commonly used for beverage delivery, parcel delivery, concrete mixing, construction debris dumping, trash compacting, and snow plowing.
LCVs are a type of combination truck that only operate in states where freight trucks exceeding 80,000 pounds are permitted. They are three- or four-unit combinations that include at least one full trailer (48 feet or less) or three short trailers.
In 1982, the US Congress passed the Surface Transportation Assistance Act (STAA) that included provisions relating to the length of truck tractor-semitrailer and truck tractor-semitrailer-trailer combinations on National Network (NN) highways or in transit between NN highways and service locations or terminals. These provisions included the following:
Some states were granted exceptions to the Federal length standards and were thus allowed to enforce higher limits before the STAA standard. These exceptions are referred to as ‘grandfathered rights;’ whereas federal laws require that states cannot legislate trailer length to be under 53 feet on the Interstate and access roads, states are free to allow trailers that are less than 53 feet on roads that aren’t funded by the federal government.
The following table is a summary of the semitrailer length laws by state:
State Maximum Trailer Length (in feet) Maximum Trailer Length (in meters) Sub-State Measures and Additional Notes Alabama 57′ 0″ 17.37 53′ 6″ maximum on roads that are less than 12′ Alaska 53′ 0″ 16.15 1) 48′ 0″ maximum on non-designated highways 2) Trailer must have kingpin-to-center distance of 41′ or less if it’s 48′ or more Arizona 57′ 6″ 17.53 53′ 0″ maximum on other (non-Interstate) highways Arkansas 53′ 6″ 16.31 Permit may be available for trailers up to 59′ 6″ long California 48′ 0″ 14.63 1) 53’ maximum for semitrailers with a kingpin-to-center distance of 40’ or less 2) No trailer length limit on California Black Routes Colorado 57′ 4″ 17.48 Connecticut 53′ 0″ 16.15 48′ 0″ maximum on non-designated State routes Delaware 53′ 0″ 16.15 Florida 57′ 0″ 17.37 Trailer must have kingpin-to-center distance of 41′ or less if the trailer is longer than 48′ Georgia 48′ 0″ 14.63 Hawaii 48′ 0″ 14.63 Idaho 53′ 0″ 16.15 48′ 0″ maximum on designated secondary highways (non-NN) Illinois 53′ 0″ 16.15 Indiana 48′ 0″ 14.63 53’ maximum permitted if 1) kingpin-to-rearmost axle distance is 40′ 6″ or less 2) kingpin-to-center distance is 45′ 6″ or less Iowa 53′ 0″ 16.15 Kansas 57′ 6″ 17.53 Kentucky 53′ 0″ 16.15 Louisiana 59′ 6″ 18.14 Maine 53′ 0″ 16.15 48′ 0″ maximum on non-53′ network Maryland 53′ 0″ 16.15 1) 48′ 0″ maximum on non-designated highways 2) Kingpin-to-center distance should not exceed 41′ for trailers longer than 48′ Massachusetts 53′ 0″ 16.15 Michigan 53′ 0″ 16.15 48′ maximum on non-designated highways Minnesota 53′ 0″ 16.15 Mississippi 53′ 0″ 16.15 Missouri 53′ 0″ 16.15 Montana 53′ 0″ 16.15 Nebraska 53′ 0″ 16.15 Nevada 53′ 0″ 16.15 New Hampshire 53′ 0″ 16.15 48′ 0″ maximum on non-designated highways New Jersey 53′ 0″ 14.63 48′ 0″ maximum on State roads other than the 102″ network New Mexico 57′ 6″ 17.53 New York 53′ 0″ 16.15 1) 48′ 0″ maximum on non-qualifying highways 2) Trailers exceeding 48′ must have kingpin-to-rear axle center setting of 43′ or less North Carolina 53′ 0″ 16.15 48′ 0″ maximum on non-designated highways North Dakota 53′ 0″ 16.15 Ohio 53′ 0″ 16.15 Oklahoma 59′ 6″ 18.14 53′ 0″ maximum on State roads Oregon 53′ 0″ 16.15 Pennsylvania 53′ 0″ 16.15 Kingpin-to-rear axle center must not exceed 41′ Rhode Island 53′ 0″ 16.15 1) 48′ 0″ maximum on non-Interstate routes 2) Kingpin-to-rear axle center must not exceed 41′ South Carolina 53′ 0″ 16.15 Kingpin-to-rear axle center must not exceed 41′ South Dakota 53′ 0″ 16.15 Tennessee 53′ 0″ 16.15 Kingpin-to-end of trailer or load must not exceed 50′ Texas 59′ 0″ 17.98 Utah 53′ 0″ 16.15 1) Permit available for trailers up to 57′ 0″ long 2) 48′ 0″ maximum on non-designated roads Vermont 53′ 0″ 16.15 1) 48′ 0″ maximum on non-designated highways 2) For 53′ 0″ trailer, kingpin-to-rear axle center setting should not exceed 43′ Virginia 48′ 0″ 14.63 Up to 53′ 0″ trailer allowed as long as kingpin-to-rear tandem center does not exceed 41′ Washington 53′ 0″ 16.15 Permit available for longer trailers up to 56′ 0″ West Virginia 53′ 0″ 16.15 48′ 0″ maximum on non-designated highways Wisconsin 53′ 0″ 16.15 48′ 0″ maximum on non-designated highways Wyoming 53′ 0″ 16.15 48′ 0″ maximum on non-designated highwaysTable via U.S Department of Transportation
The STAA rules only apply to truck-tractor semitrailer and truck-tractor semitrailer-trailer combinations. Certain specialized commercial motor vehicles (CMV) are subject to a different set of length rules. Notable specialized vehicles include automobile transporters, boat transporters, and truck-tractor semitrailer combinations. The length requirements of these vehicles are as follows.
Note that length provisions for automobile transporters and boat transporters exclude the front and rear overhang. No state shall impose a rear overhang of under 4 feet or a front overhang of under 3 feet.
Semitrailers are often the most cost-effective means of moving goods from one point to another. However, as you cross state borders, a trailer length that is perfectly legal in one state could be prohibited in another. Familiarizing yourself with semitrailer length laws by state will help you avoid running into any unpleasant legal surprises.
At Hale Trailer, our commercial trailer experts are prepared to help you through the whole trailer rental or purchasing process. For any questions about semitrailer length laws, don’t hesitate to contact us for more information.
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