Longer Combination Vehicles

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What are longer combination vehicles? Longer combination vehicles, commonly called "LCVs," are tractor-trailer combinations with two or more trailers that may exceed 80,000 pounds gross vehicle weight (GVW). LCVs typically include three vehicle types:

WEIGHT (lbs)
Rocky Mountain Double
Turnpike Double
Triple Trailer

Are LCVs allowed in California? LCVs are not allowed on California interstates and State routes. LCVs may operate on local streets and roads with permits from local jurisdictions.

Would California consider allowing LCVs? At this time, California cannot allow LCVs on interstates and other federally funded highways because of a federal freeze preventing an increase in the size and weight of combination vehicles. (See "Legal History" below.) Local jurisdictions may allow oversize/overweight vehicles on highways they are responsible for by permit, per Vehicle Code 35558.

During the 2003-2004 legislative session, Senate Joint Resolution (SJR 7) memorialized the President and Congress to maintain the current federal truck size and weight limitations, and to oppose proposals to experiment with longer and heavier trucks on public highways in the reauthorization of the federal SAFETEA-LU.

Where are LCVs allowed in the U.S.? Per ISTEA, LCVs are allowed by a grandfathering clause only in states where they were in operation before June 1, 1991. Some form of LCV is currently allowed on designated routes in Alaska, Arizona, Colorado, Florida, Idaho, Indiana, Iowa, Kansas, Massachusetts, Michigan, Missouri, Montana, Nebraska, Nevada, New York, North Dakota, Ohio, Oklahoma, Oregon, South Dakota, Utah, Washington, and Wyoming. Oversize/Overweight vehicles may be allowed by local jurisdictions in California for certain vehicles and loads.


What federal laws cover LCVs? In 1956, federal regulations gave California and more than 20 other states the option to allow triple trailers and other long vehicles. However, California did not exercise that option. Then, in 1991, Congress passed the Intermodal Surface Transportation Efficiency Act (ISTEA) which prohibited the states from increasing the size and weight of combination vehicles beyond that already allowed on June 1, 1991. The ISTEA prohibition is reflected in US Code Title 23 Section 127 (d) and in the Code of Federal Regulations, Title 23, Section 658.23.

What state laws cover LCVs?

California Legal: The California Vehicle Code (CVC) Section 35401(a) states that no combination of vehicles may exceed a length of 65 feet. This section does not mention the maximum number of vehicles allowed. (However, Section 21715 limits the number of trailers to one if the towing vehicle is a passenger vehicle, or if the towing vehicle is under 4,000 pounds unladen.)

California Legal: CVC Section 35401(b)(1) states that a truck tractor, a semitrailer, and a semitrailer or trailer may not exceed 75 feet if neither the semitrailers nor the trailer exceeds 28 feet 6 inches. This section limits this particular combination to two trailers.

STAA: Section 35401.5(a)(2) states that, for a truck tractor, semitrailer, and trailer combination that uses the National Network and the Terminal Access and Service Access routes exclusively (a STAA vehicle), the overall length can be unlimited, but neither the semitrailer nor the trailer may exceed 28 feet 6 inches. This section limits this particular combination to two trailers.

For more information on legal truck dimensions in California, see the fact sheet Truck Sizes & Routes.


The advantages of LCVs may include:

  • Productivity: LCVs improve productivity due to an increase of cargo-carrying capacity of 30% to 100% per driver. This results in fewer truck trips, lower cost, and fewer miles driven.
  • Cost: Transport costs may be lower due to fewer drivers needed per cargo unit, and more efficient use of fuel. The cost savings may be passed on to the consumer, or increase profits.
  • Traffic: Improved productivity may result in fewer trucks on the road.
  • Air Emissions: LCVs may produce lower air emissions per unit of cargo transported.

The disadvantages to LCVs may include:

  • Safety: Large trucks are involved in a disproportional percentage of fatal collisions. However, statistics on LCVs are difficult to obtain because of the low number of vehicle involved. Triples tend to sway and can leave the lane they are traveling in, although sway can be lessened by advanced connector types. Triples also require more passing length, spray more rain and snow, and have a history of being underpowered while climbing steep grades.
  • Pavement Damage: Heavier trucks deteriorate the pavement structure at an accelerated rate. A study at University of Texas found that one big rig pass causes the damage equivalent to 2,000 to 3,000 cars. However, the extra pavement damage from LCVs may be mitigated by the increased number of axles.
  • Infrastructure Damage: LCVs, especially Turnpike Doubles and Rocky Mountain Doubles, demonstrate wider off-tracking on curves than currently legal tractor-trailer combinations. Off-tracking can damage shoulders, curbs and roadside signs along ramps and intersections.
  • Parking: The parking spaces at State rest areas and truck stops are not designed for trucks longer than 80 feet.
  • Traffic: In theory, LCVs could result in fewer trucks on the road; however, if rail cargo is diverted to trucks due to lower costs, then any traffic advantage would be negated.


Have LCVs been tested in California? Yes. In 1983, Caltrans tested and videotaped the performance of each LCV type on California highways along the same 1,200 mile route. The test also included freeway interchanges, open-road travel, urban traffic, narrow lanes, two-lane roads, rest areas, weigh scales, off-tracking, speed on grades, braking, acceleration, travel in rain and wind, noise generation, and fuel economy. Some of the problems encountered included (1) the whip and sway action of the Triples on the open road, (2) the off-tracking of the Rocky Mountain Doubles and Turnpike Doubles on curves, and (3) the difficulty parking in rest areas of all three LCV types. More about LCV Operational Test.

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