Triple trailers are legal in about ten states, nearly all in the western half of the country, and only on designated routes with the right permit. Three more states allow them under narrow federal exceptions. Everywhere else, triples are barred by a 1991 federal law that froze the map in place: if a state wasn’t already running triples on June 1, 1991, it generally cannot start now. The states that do allow them set their own weight ceilings, length limits, and permit rules, so what’s legal in Montana at 131,060 pounds is not legal in Oklahoma at 90,000.
The States That Allow Triple Trailers
Ten states have active triple-trailer operations on designated routes. Maximum lengths, gross weights, and permit requirements vary:
- Colorado — up to 115.5 feet, 110,000 lbs. Annual permit required.
- Idaho — up to 95 feet, 105,500 lbs. Annual permit required.
- Kansas — up to 109 feet, 120,000 lbs. Special Vehicle Combination permit required, limited to I-70 between the Colorado state line and Exit 19.
- Montana — up to 100 feet, 131,060 lbs. Annual or single-trip permit required.
- Nevada — up to 95 feet, 129,000 lbs. Permit required.
- North Dakota — up to 100 feet, 105,500 lbs.
- Oklahoma — up to 95 feet, 90,000 lbs. Permit required for all combinations.
- Oregon — up to 96 feet, 105,500 lbs. Permit required if gross vehicle weight exceeds 80,000 lbs.
- South Dakota — up to 100 feet, 129,000 lbs. Permit required above 80,000 lbs.
- Utah — up to 95 feet, 129,000 lbs. Permit required.
These ten states form the core of triple-trailer territory and are heavily used by less-than-truckload carriers moving freight between western terminals.1Federal Highway Administration. Western Uniformity Scenario Analysis Chapter 2 – Scenario Description
States With Narrow or Limited Triple-Trailer Authority
Three more states allow triples under exceptions written directly into federal law at 23 U.S.C. 127(d):
- Alaska permits triples that were in actual operation before July 5, 1991, extending the usual June 1 cutoff by about five weeks.
- Iowa allows triples only on Interstate 29 between Sioux City and the South Dakota border and on Interstate 129 between Sioux City and the Nebraska border.
- Ohio permits triple combinations using three 28.5-foot cargo units on a single one-mile segment of Ohio State Route 7 south of Exit 16 on the Ohio Turnpike.
A few other states appear in triple-trailer discussions but don’t practically count. Arizona has weight data on file for triples up to 129,000 pounds, but FHWA has noted the allowance covers only a very small corner of the state. Nebraska permits only empty triples on a very limited network, and the most recent federal study found no triple operations actually taking place there. Florida allows certain multi-trailer combinations on state roads, but they cannot operate on the Interstate System and cannot exceed 80,000 pounds, so they don’t qualify as longer combination vehicles under federal law.2Federal Highway Administration. Federal Size Regulations for Commercial Motor Vehicles
States Sometimes Listed But Not Actually Open to Triples
Washington and Wyoming are occasionally included in triple-trailer lists, but FHWA data confirms neither currently permits triples on their highways.1Federal Highway Administration. Western Uniformity Scenario Analysis Chapter 2 – Scenario Description Wyoming has a special federal provision allowing it to authorize additional LCV configurations up to 117,000 pounds if those configurations were approved by state law before November 3, 1992, but the state has not used that authority for triples.3Federal Highway Administration. Title 23, United States Code Every state not named above is barred from introducing new triple-trailer operations.
Why The Map Is Frozen
Section 4006 of the Intermodal Surface Transportation Efficiency Act of 1991 froze the maximum size and weight of longer combination vehicles to whatever each state had lawfully running on a regular or periodic basis as of June 1, 1991. The freeze locked in specific vehicle configuration types, routes, and operating conditions, not just gross weight.4Office of the Law Revision Counsel. Public Law 102-240 – December 18, 1991
Codified at 23 U.S.C. 127(d), the rule allows a longer combination vehicle to continue operating only if that configuration type was authorized by state law and in actual lawful operation on or before the cutoff date. States cannot claim a configuration was authorized merely because a broad permit statute could have covered it. The configuration had to actually be on the road.3Federal Highway Administration. Title 23, United States Code Grandfathered operations remain subject to at least the same state restrictions in force on June 1, 1991. States can make minor, temporary route adjustments for safety or road construction, but they cannot expand access to new highways or raise maximum weights beyond what was frozen. No legislation since has reopened the map, and it has been essentially static for more than three decades.
Permits and Designated Routes
Nearly every state that allows triples requires a permit, and most permits restrict the combination to specific interstate segments or state highways. The list of legal LCV routes on the Interstate System is maintained by the Federal Highway Administration in Appendix C to 23 CFR Part 658. If a state further restricts or eliminates LCV routes after June 1, 1991, it must notify FHWA within 30 days, and the agency publishes the change as an amendment.5GovInfo. 23 CFR 658.23 – LCV Route Designations
Permit formats differ. Colorado, Idaho, Nevada, and Utah use annual permits. Montana offers both annual and single-trip permits. Kansas requires a Special Vehicle Combination permit tied to the I-70 corridor near the Colorado border. Oregon only requires a permit when the triple combination exceeds 80,000 pounds, because below that threshold the combination isn’t technically an LCV under federal law.1Federal Highway Administration. Western Uniformity Scenario Analysis Chapter 2 – Scenario Description Fee schedules vary by state and aren’t published in a single federal source, so carriers should contact each state’s department of transportation directly. Many state DOTs post downloadable route maps and maintain hotlines for current size, weight, and construction restrictions.
Driver Credentials Required To Operate A Triple
Running a triple trailer takes two separate credentials, not one. The first is a doubles/triples (T) endorsement on a valid Class A commercial driver’s license. The T endorsement requires passing a written knowledge test — no behind-the-wheel skills test — covering assembly and hookup, placement of the heaviest trailer, handling characteristics like off-tracking and oscillatory sway, and traffic effects such as longer passing times and splash-and-spray on nearby drivers.6eCFR. 49 CFR Part 383 – Commercial Driver’s License Standards
The second requirement is a longer combination vehicle training program under 49 CFR Part 380. A T endorsement alone is not enough to operate a triple. To qualify for the training, a driver must already hold a valid Class A CDL with the T endorsement and, during the six months immediately before applying, must have experience operating a tractor/semi-trailer combination or a tractor/semi-trailer/trailer combination at or below 80,000 pounds. The record must be clean: no CDL suspensions, no major offense convictions, no out-of-service-order violations, and no more than one serious traffic violation while operating a commercial vehicle.7eCFR. 49 CFR 380.205 – LCV Triples
The LCV training program itself includes classroom instruction and behind-the-wheel training on the actual vehicle type. The driver has to pass a knowledge test with at least an 80 percent score and a skills test demonstrating every maneuver practiced during instruction. Failing to obey traffic laws during the skills test, or being involved in a preventable crash, is automatic failure.8eCFR. 49 CFR Part 380 – Special Training Requirements
Penalties For Running Triples Where You Shouldn’t
Operating a triple trailer on a non-designated route or without the required permit carries consequences at both the federal and state level. The Federal Motor Carrier Safety Administration can impose a civil penalty of up to $11,000 per violation against a carrier and up to $2,750 against an individual driver for failing to comply with a posted route restriction.9FMCSA. What Is the Penalty for Failing to Comply With a Posted Route Restriction Along a Roadway
State penalties stack on top. Amounts vary; Alaska, for example, sets a bail amount of $500 for operating triples without a permit. More consequentially, the issuing agency in many states can suspend or revoke an existing LCV permit for cause, which can shut down a carrier’s triple-trailer operations in that state. Being barred from a key corridor like Nevada or Utah can ripple across an entire western freight network. Overweight violations compound the problem: a triple caught on a non-permitted route and over its weight limit draws fines for both, calculated per the applicable state schedule, and repeat violations raise the odds of permit revocation and FMCSA compliance reviews that affect the carrier’s safety rating.