New Hampshire OS/OD Overview
Permit Required
Yes – any load exceeding legal size or weight requires a permit from the New Hampshire Department of Transportation (NHDOT).
Legal Limits (Without Permit)
- Width: 8'6"
- Height: 13'6"
- Length: 76' (combo); 53' trailer allowed with conditions
- Weight: 80,000 lbs GVW (with standard axle limits)
Permitted Load Maximums (Typical Upper Limits)
- Width: Up to 16' with escort
- Height: Over 14' requires route survey and utility clearance
- Length: Over 120' requires special routing and escort
- Weight: Over 130,000 lbs requires detailed axle data and bridge review
Superloads must be coordinated through NHDOT’s Permit Office and may involve multiple agencies.
Travel Hours
- Standard: ½ hour before sunrise to ½ hour after sunset
- Weekend: No travel after noon on Saturday or anytime Sunday
- Holidays: No movement on state holidays or after noon the day before
- Night travel: Rare and only allowed with special permission for smaller loads
Escort Requirements (General Guidelines)
| Dimension | Escort Requirement |
|---|---|
| Width > 12' | 1 Escort (typically front or rear based on route) |
| Width > 14' | 2 Escorts (front and rear) |
| Height > 14' | High pole escort and utility coordination |
| Length > 120' | 1 or more Escorts depending on configuration |
Additional Notes
- All oversize loads must display “Oversize Load” signs, red/orange flags, and amber lights
- Mountain routes and older infrastructure may require alternate routing
- Permits issued through the NHDOT Permit Office (paper or email submission; no full online system as of now)
Detailed Information
PERMITS: Permits valid for five travel days. Must have permit prior to entering the state.
OPERATING TIME: One-half hour before sunrise to one-half hour after sunset, Monday through Friday. No weekend or holiday travel for overdimensional loads. Overweight only are not restricted for travel time.
RESTRICTED TRAVEL: Travel through the city of Manchester is restricted during the hours of 7:00 a.m. – 9:00 a.m. and 3:00 p.m. – 6:00 p.m. Toll road requirements are the same as other highways. No travel on major holidays, including some holiday weekend restrictions.
LEGAL DIMENSIONS: Width: 8'6" Height: 13'6" Length: 53' semi-trailer on Interstate and designated highways (41' Kingpin to center of rear tandem). 48' on all other roads. Length limitations do not apply to vehicles transporting poles, pipes, logs, timbers, steel beams (not for stretch trailers) Weight: 80,000 Gross Single – 20,000 designated highways* (22,400 other roads) Tandem – 34,000 designated highways* (36,000 other roads) Tridem – Same as tandem * When GVW isn't over 73,280 pounds, 22,440 pounds legal on a single axle, and 36,000 on a tandem.
ROUTINE PERMIT LIMITS: Width: 16' Height: 16' Length: 110' Weight: Single – 25,000 Tandem – 50,000 Tridem – 70,000 Quad – 85,000 Loads exceeding these dimensions are treated as super loads. A bridge review is required when: any single axle exceeds 27,500 pounds, any axle of a tandem exceeds 25,000 pounds, any axle of a tridem exceeds 22,500 pounds, any axle of a quad exceeds 20,000 pounds, any 5-axle combination exceeds 100,000 pounds, any 6-axle combination exceeds 120,000 pounds, any 7-axle combination exceeds 130,000 pounds, any combination of 8 or more axles exceeds 149,999 pounds.
ESCORTS: Width: At 12' – 1 escort; over 15'1” – 1 State Police escort (need 48 hours notice). State may require a second escort for some routes. Height: Route survey is be required for over 13'6 high, escort not usually required for height. Overhang: Over 15' – 1 escort. On a 2-lane undivided highway, 2 escorts are required if overhang exceeds 15' and width is over 12'. Length: At 80' – 1 escort; over 100' – 1 State Police escort (need 48 hour notice) unless they exempt it.
SIGNS, FLAGS & LIGHTS: "Oversize Load" sign required on front of an oversize vehicle and on the rear of the vehicle or load, whichever provides the best rear display. Mount red flags (at least 12" square) on all extremities of the load when load extends over sides of trailer more than 4 inches. When rear overhang exceeds 4', 1 flag shall be displayed at the end of the overhang if less than 2' wide, and 2 flags if the overhang is over 2' wide. There are no special lighting requirements.
SEASONAL LOAD RESTRICTIONS: During spring thaw, weights may be limited to 20,000 gross axle weight or less.