Oversize Loads in Maryland: Lowboy & Multi‑Axle Trailer Guide

Hauling oversize or overweight loads in Maryland comes with zero margin for error. Operators must navigate strict size and weight thresholds, mandatory permits, low-clearance routes, and federal axle-spacing rules. 

Maryland’s roads add real-world pressure. Between Chesapeake crossings and Baltimore tunnels, a normal haul can turn into a puzzle if you miss a clearance, curfew, or axle spacing detail. The play is simple. Know the limits from the Code of Maryland Regulations (COMAR), follow the General Conditions for Hauling Permits, then match your trailer to the problem. If height is tight, go lowboy. If weight and group spacing are tight, go multi-axle.

Maryland’s Oversize and Overweight Rules

The Permit Manual sets the baseline at 102 inches wide, 13 ft 6 in high, and (for common tractor-semi moves on designated routes) standard trailer lengths with 53 ft allowed on the truck network. The maximum gross vehicle weight is 80,000 lbs, and Maryland applies the federal bridge formula in state law for axle groups.

When Permits Are Required

Anything over those baselines needs a permit. Maryland also makes it clear that permits are a privilege. If a load can be divided to meet legal size or weight, you are expected to divide it. Misstatements on applications or moving without the proper permit can lead to suspension or revocation, and serious overweight can require unloading on the spot.

Permit Types and Costs

According to the Code of Maryland Regulations (COMAR) Title 11, Subtitle 04, Chapter 01 (“Permits for Oversize and Overweight Vehicles”), the State Highway Administration issues seven types of permits for oversize and overweight moves. These permits set the conditions, weight and dimension limits, and fees that govern all permitted moves in Maryland.

• Special Hauling Permit: For a single one-way trip. Fees start at $30 for 40 tons (80,000 lbs) or less, with $5 added for each ton (or part of a ton) above 40 tons.
• Book Permits: Issued in sets of ten single-trip permits. Each permit covers one trip (and the return of an empty oversize vehicle if within legal weight). Valid for two years. Limits: 85 ft length, 13 ft width, 15 ft height, 45 tons GVW.
• Blanket Permits: Available for 30 days ($50) or 1 year ($500). Caps: 75 ft length, 12 ft width, 14 ft height, and up to 45 tons (90,000 lbs) for special mobile equipment.
• Containerized Cargo Permits: For sealed, international freight in seagoing containers moving to/from the Port of Baltimore. GVW capped at 90,000 lbs under specific axle rules.
• Special Vehicle Permits: For controlled, one-time moves of a unique vehicle that cannot meet legal limits or qualify as special mobile equipment.
• Exceptional Hauling Permits: For certain commodities (milk, forestry products). Require a six-axle minimum and at least 50 ft centerline spacing between front and rear axles.
• Heavy Weight Port Corridor Permits: For specified routes in and around the Port of Baltimore, authorizing certain heavy containerized loads under defined limits.
  

Low-Clearance Routes and Axle-Spacing Essentials

Maryland’s infrastructure adds unique challenges. The Maryland Oversize/Overweight Hauling Permit Manual explains that any load taller than 14 ft 6 in requires a mandatory clearance survey. Oversized and hazardous loads are restricted from the Fort McHenry Tunnel (I-95) and Baltimore Harbor Tunnel (I-895), with detours usually routed via the I-695 Beltway.

General Conditions

These conditions are published jointly by the Maryland State Highway Administration and the City of Baltimore, and they apply to all permitted moves.

• A state permit does not cover city, county, or municipal roads, or railroads. If your route leaves state-maintained highways, set up approvals with the local jurisdiction or railroad. Any damage to public infrastructure is on the permittee.
• Keep the permit in the vehicle and present it to officials or anyone involved in an incident.
• Protect public traffic. Arrange flaggers or police in advance when crossing narrow bridges.
• Do not start a move that will disturb wires, signals, tree limbs, or other overhead structures until you have permission and coordination with the owners.
• No overweight permits for divisible loads. Strip removable weight. Reduce oversize dimensions where possible.
• Permits are valid only with favorable road and weather. They are not valid during a snow emergency.

Tunnels and Toll Facilities

The Baltimore Harbor Tunnel (I-895) does not take permit loads except containerized cargo with a valid permit. The Fort McHenry Tunnel (I-95) has strict restrictions that often block oversize moves. The Permit Manual requires you to notify certain Maryland Transportation Authority facilities one hour before crossing and follow posted rules.

Bridge Formula and Axle Configurations

Maryland uses the federal Bridge Formula baked into state law to control how much weight a truck can carry based on axle count and spacing. The idea is simple. More axles and more distance between them spread the load so bridges and pavement are not overstressed.

The Permit Manual includes example patterns used for heavy combinations on interstate routes. Typical cases for 120,000 to 150,000 lbs can avoid a separate bridge review when all spacing rules and per-axle caps are met. Examples from the manual include:

• A single non-steer axle up to 27,000 lbs and a steer axle up to 20,000 lbs.
• Tandem axles 4 to 8 feet apart up to 26,000 lbs per axle.
• Tridem axles 4 to 8 feet apart up to 21,000 lbs per axle.
• A main spacing of at least 30 feet between major axle groups.

Route Checks and Who to Call

The Permit Manual lists the Hauling Permits Unit and relevant MdTA facilities with instructions to call ahead one hour before certain crossings. If your route touches beltways, toll bridges, or tunnels, coordinate in advance and follow any posted lane or timing instructions on your permit. Keep contact numbers handy in the cab with the permit.

Choosing the Right Trailer: Lowboys vs. Multi-Axle

The type of trailer you choose determines whether your permit gets approved or denied.

Lowboy Trailers: Managing Height

Lowboys use a double-drop deck design that lowers the center of gravity and keeps tall loads within the legal 13 ft 6 in height. Once a load exceeds 14 ft 6 in, Maryland requires a clearance survey. Lowboys help operators avoid that extra step by keeping equipment under the threshold.

Multi-Axle Trailers: Distributing Weight

When weight is the issue, multi-axle trailers spread the load across additional points, aligning with the Federal Bridge Formula. Proper axle spacing is a condition of permit approval under Maryland’s rules, and multi-axle rigs are often the only way to move heavy equipment like 100,000+ lbs machinery legally.

Match your trailer to the issue:

• Height problem? Use a lowboy
• Weight or bridge compliance issue? Use multi-axle

Quick-Reference Chart: Maryland Oversize Rules

Category	Legal without permit	With permit allowed under the Manual
Width	up to 8 ft 6 in	Over 8 ft 6 in requires a permit. One private escort at 13 ft. Two private escorts at 14 ft or more.
Height	up to 13 ft 6 in	14 ft 6 in requires a height pole. 16 ft or higher can require district approval, State Police escort, and SOC notice.
Length	Standard tractor-semi lengths; 53 ft trailers on the network	Over 85 ft needs one private escort. 100 ft or longer limited to 9:00 a.m. to 3:30 p.m. on beltways and needs one escort. 120 ft or longer special escort. 140 ft or longer two escorts and district approval.
GVW	80,000 lbs	Over 45 tons limited to 9:00 a.m. to 3:30 p.m. on beltways. Over 60 tons can require special and police escorts plus approvals.
Axle groups	Governed by bridge formula	Heavy examples from the Manual include single non-steer 27,000 lbs, steer 20,000 lbs, tandem 4–8 ft 26,000 lbs per axle, tridem 4–8 ft 21,000 lbs per axle, with ≥ 30 ft main spacing between major groups.
Hours	Daylight moves only	Daylight only statewide. No moves Sunday or after 12:00 p.m. Saturday. On MdTA facilities, added restriction Friday 12:00 p.m. to Monday 9:00 a.m.
Holidays	n/a	No travel on New Year’s Day, Memorial Day, Independence Day, Labor Day, Thanksgiving Day, Christmas Day.

Maryland hauling requires strict attention to legal size, weight, and routing rules. Violations can mean delayed shipments, fines, or revoked permits. The right trailer choice—lowboy for height or multi-axle for weight—ensures compliance and keeps your load moving.