Maine Semitrailer Length Limit

Maine sits at the 48-foot federal floor in Appendix B. No grandfathered length above it — what you can actually run comes from Maine state law, which like most states is 53 feet.

Appendix B length48'0"

Federal floor48'0" (all states)

Kingpin conditionNone

Tractor + 2 unitsNot allowed

Tractor + 3 unitsNot allowed

This is a floor, not your length limit. Appendix B lists what a state was grandfathered to keep under the STAA of 1982 and must go on allowing on the National Network. It is not the state's own limit, and it is not permission to run that length on any road you like. Most states allow 53-foot semitrailers under their own law — that permission comes from state statute, not from this table — and every state can still restrict length on specific routes, in cities, and off the National Network. Use this to know the federal baseline, then check the state limit and the route.

01 The rule

What Maine has to allow

Nothing was grandfathered above the floor here, and that is not the same as a 48-foot limit. It means the federal table protects nothing beyond 48 feet in Maine; whatever Maine allows above it — 53 feet in most states — comes from Maine's own statute and can be changed by Maine.

The number comes from 23 CFR Part 658 Appendix B, the STAA grandfather list. It binds Maine on the National Network and cannot be lowered. It says nothing about what Maine allows beyond it, which is where state law takes over.

02 The details

Length, kingpin and combinations

Appendix B semitrailer length: 48'0" (the federal floor)
Kingpin-to-rear-axle condition: None in Appendix B for this state.
Tractor plus two trailing units: not allowed
Tractor plus three trailing units: not allowed
Other grandfathered combinations: not allowed
Past the legal length: a Maine oversize permit — see Maine oversize permits.

Maine Trailer Length FAQ

What is the legal trailer length in Maine without a permit?

The federally protected length on the National Network is 48'0" (23 CFR 658 Appendix B). That is the 48-foot floor every state must allow. Maine state law sets what you can actually run, and for most states that is 53 feet.

Can I run a 53-foot trailer in Maine?

Appendix B only protects 48'0" in Maine. 53-foot trailers are common there under Maine state law, but that permission is state statute, not this federal table — confirm the current Maine limit and any route restriction.

Are doubles or triples allowed in Maine?

Maine has no grandfathered LCV rights in Appendix C. Standard STAA doubles only — no long doubles, no triples.

Does this length apply on every road in Maine?

No. Appendix B binds the National Network — the Interstates plus the designated primary routes. Off the network, and inside cities, Maine can and does restrict length, and posted route restrictions still apply. Check the route as well as the number.

Reference information for planning, not legal advice. Traffic laws change and this can be out of date, so always confirm the current statute and obey posted signs before you rely on it. Last reviewed July 2026. Source: eCFR, 23 CFR 658 Appendix B and C (title 23 as of 2026-07-23). See our Terms & Disclaimer.

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Maine Semitrailer Length Limit

What Maine has to allow

Length, kingpin and combinations

Maine Trailer Length FAQ

More for Maine

Maine Weight Limits

Maine Oversize Permits

Maine 511

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Check Maine before you roll