Motor carrier classes by state
New Hampshire does not have a weight law. It has three of them, running in parallel, and which one governs a given truck on a given day depends on the surface under the wheels and on a certificate in the cab. The same three-axle dump truck is capped at 47,500 pounds on the interstate, 55,000 pounds on every other way in the state, and 65,000 pounds if the Department of Safety has certified it — three lawful gross weights for one vehicle, from three separate sections of RSA chapter 266.
Most states answer the weight question once and then carve exceptions out of the answer. New Hampshire wrote the answer three times. RSA 266:18 governs the interstate and defense highway system. RSA 266:18-a governs every other way in the state — which is the surface aggregate work actually runs on. RSA 266:18-b governs vehicles that have bought their way into a higher schedule through a separate certification.
That structure changes what a fleet file needs to contain. The governing number is not a property of the truck alone. It is a property of the truck, the road class it is on, and whether a piece of paper from the Department of Safety is current — and the third of those expires on the sale or transfer of the vehicle, which makes it a fleet-roster question rather than a one-time filing.
Layered on top is a municipal regime that decides where a loaded truck may go at all. New Hampshire towns may post Class IV, V and VI highways more restrictively than the state schedule, and the statute that lets them do it also builds in a restoration duty, a hardship exemption a business can demand, and a hearing deadline that runs against the town rather than against the hauler.
A load that is lawful on a state highway can therefore become unlawful at the town line without any figure on the truck having changed.
Running aggregate on New Hampshire town roads? Tell us which units carry an RSA 266:18-d certification and which towns your pits and jobs sit in — those two facts decide both the lawful weight and the lawful route.
RSA 266:18 opens by prohibiting the driving “on the interstate and defense highway system of this state” of any vehicle exceeding its limits. RSA 266:18-a opens by prohibiting the driving “on ways of this state, other than on the interstate and defense highway system as provided by RSA 266:18” of any vehicle exceeding its limits. The two sections name each other, and between them they divide every mile of pavement in the state into two regimes.
The gross weight tables diverge sharply, and they diverge in the direction that matters to a dump operator. A single unit three-axle vehicle is capped at 47,500 pounds under RSA 266:18, II(b) on the interstate system, and at 55,000 pounds under RSA 266:18-a, II(b) off it. A single unit four-axle vehicle runs 47,500 on the interstate and 60,000 off it. A two-axle vehicle is 33,400 pounds under both.
So the interstate is the restrictive surface here, not the permissive one. A tri-axle loaded to 55,000 pounds is legal on the state and town road network and 7,500 pounds over on the ramp. That reverses the intuition most operators bring from states where the interstate carries the highest allowance.
RSA 266:18-b is the third regime and it is conditional on paperwork rather than geography. Its opening sentence limits it to vehicles “certified pursuant to RSA 266:18-d” and to driving “on any way other than the interstate and defense highway system.” Under it a single unit three-axle vehicle takes 65,000 pounds, a four-axle takes 73,000, and a two-axle takes 37,400.
Each section also states its own axle allowances rather than importing a common table. RSA 266:18 splits its axle figures internally at a gross weight of 73,280 pounds — 22,400 pounds per axle on three-axle single unit vehicles and on other vehicles with axles ten feet or more apart at or below that gross, with the figures dropping above it. RSA 266:18-a carries only the lower-gross tier, at 22,400 and 18,000 pounds. RSA 266:18-b states its own: 22,400 per axle on three-axle single unit vehicles, 20,000 per axle on four-axle single unit vehicles, and 22,400 on other vehicles with axles ten feet or more apart. Across all three, two axles less than forty inches apart count as a single axle unit.
The third schedule is unlocked by an instrument that is not an oversize permit and is not issued by the same agency. RSA 266:18-d, I provides that no vehicle shall be driven on any way with a gross vehicle weight in excess of the RSA 266:18-a limits “without having obtained a certification therefor from the commissioner of the department of safety.” Special permits under RSA 266:24 come from the commissioner of transportation; this comes from Safety, and it is a standing status rather than a movement authorization.
Paragraph II sets the price and the term: “The application shall be accompanied by an additional fee of $105 and the certification shall be in effect for a period of one year. The certification shall expire upon the sale or transfer of the vehicle. The certification shall cover a power unit and not more than one trailer.” The expiry-on-transfer clause is the one that catches fleets — a certified unit sold mid-term takes its certification off the road with it, and the buyer starts over.
Paragraph III is where the engineering enters. Certification requires documentation satisfactory to the department, from the manufacturer, attesting that the vehicle is capable of safely carrying the additional weight. A fresh attestation is required “at any time when the configuration of the vehicle relative to power unit, axles, springs, or other safety items that could affect the vehicle’s ability to qualify for an excess weight certification is altered.” The attestation must designate the maximum safe gross weight “as determined by the components and the summation of the manufacturer’s axle design limits for each axle of the vehicle.”
That is a rare thing in a state weight statute: a legal ceiling defined by the sum of the manufacturer’s own axle design limits rather than by a legislative table alone. It also means a spec change made in a shop — a spring pack, an added axle, a power unit swap — is a re-certification event, and one an operator can inadvertently skip. Paragraph V-b adds a second way the status lapses: if a vehicle is declared out of service for a safety violation or is issued a citation for an axle distance violation, “the certification shall be inoperative until the condition has been rectified.”
Paragraph V makes the certified vehicle eligible for an additional registration, whose fee is set by the ordinary registration fee statute and charged on top of the $105. Paragraph V-a requires out-of-state carriers on apportioned registration who want the additional weight to comply with the section and be registered for the weight they are certified to carry. Paragraph IV supplies a reciprocity rule that reaches ordinary operation rather than permitted moves: a certified vehicle “shall be considered to have reciprocity with other states granting New Hampshire similar reciprocity for the full weight limit designated in RSA 266:18-b or the weight limit for which the vehicle is registered, whichever is less.”
Section 266:18-d as served carries source line 1986, 121:3; 2004, 56:1; 2009, 28:1, 2; 2012, 171:13; 2025, 141:245, 246, effective January 31, 2026. Paragraph VI lets the commissioner or a designee revoke or suspend an additional registration where the vehicle is driven in violation of the RSA 266:18-b limits or any other provision of law, as evidenced by a record of such violations, under rules adopted pursuant to RSA 541-A.
New Hampshire states an enforcement tolerance inside the weight statute itself rather than leaving it to practice. RSA 266:18-a provides in its opening sentence that “any police officer shall allow on any way other than the interstate and defense highway system a tolerance of 5 percent above said limitations.” The word is shall, and the tolerance is scoped to non-interstate ways — the same ways the section governs.
RSA 266:18-b restates the tolerance for certified vehicles and widens it on the axle side: an officer shall allow “a tolerance of 5 percent above said limitations and 10 percent above said limitations on the axle weights.” A certified truck therefore carries a higher schedule and a wider allowance on top of it, which compounds — five percent on a 65,000 pound gross is a materially different figure from five percent on 55,000.
The certified schedule also brings load distribution rules that the other two sections do not contain, and they constrain how the allowance may be used. Under RSA 266:18-b, II(d), no single axle of a tandem unit may support more than 60 percent of the total weight supported by the tandem, and no single axle of a tri-axle unit may support more than 40 percent of the tri-axle’s total. A tandem is spared that test where neither axle exceeds the weight legally allowed on a single axle unit for the same vehicle.
The third distribution rule reaches an equipment decision directly: “The allowable gross weight of a vehicle shall not be increased by the addition of a trailing axle, so called, unless the trailing axle supports at least 50 percent of the added weight permitted by the addition of that trailing axle.” Adding an axle buys nothing unless the axle actually carries half of what it bought. That is a specification and maintenance question — air systems, ride height, equalization — before it is a scale question, and the same components sit at the center of a physical damage valuation.
Two chapter-wide provisions apply on top of all three sections. RSA 266:18-c, I and II cut permitted weights to 80 percent for a vehicle on solid rubber tires and to 40 percent on metal or other hard tires. Paragraph VI settles rounding where the distance between extreme axles is not an exact number of feet: six inches or less of excess rounds down to the stated number, more than six inches rounds up to the next higher number of feet.
We write New Hampshire aggregate and dump fleets, including units certified under RSA 266:18-d for the higher non-interstate schedule and operations working out of pits on posted town roads.
The state schedule is not the last word on a town road. RSA 231:191, I lets the governing body of a municipality establish maximum weight limits, “seasonal or otherwise,” more restrictive than the limits in RSA 266:17-26, for any Class IV, V or VI highway or portion of one, “when the highway agent determines that such highway requires postings to prevent unreasonable damage or extraordinary municipal maintenance expense.” Posting must be in accordance with currently acceptable practices and technology.
The delegation is bounded three ways and each bound matters. It reaches only Class IV, V and VI highways — the municipal classes. It runs only in the more-restrictive direction, so a town cannot raise a limit. And it is effective only where posted: paragraph II requires the limits to be posted, in the same manner as bridges under RSA 234:39 and RSA 266:18-c, “at all entrances to the restricted highway or portion of such highway from other public highways,” with signage that is legible, in a conspicuous location, and of weather resistant materials.
Because New Hampshire has no statewide frost program with published dates, zones or percentages, this is the mechanism that carries seasonal restriction in practice. The restriction exists where a town has posted it and nowhere else, and there is no state table to consult in advance. What is publishable is the architecture, not a calendar — a road-class taxonomy, a posting standard, and a named official who can let you through.
That official is named in paragraph III. Driving in violation is unlawful “without written permission provided in an expeditious manner from the selectmen or highway agent in a town, or the mayor and aldermen or street commissioner of a city,” and the names of the officials authorized to grant it “shall be posted prominently in the town office or city hall.” The same paragraph gives those officials real conditioning power: they “may impose reasonable conditions and may establish reasonable regulations for bonding and restoring the highway.”
For an aggregate operation that is the operative permission in the business. A quarry, sand pit or borrow area is generally reached by a Class V or VI road, so the first and last mile of nearly every load runs on exactly the surface a town may post. RSA 231:190 acknowledges the tension in terms, finding that important sectors of state commerce depend “in part” on efficient vehicle transport of unprocessed natural resources across Class IV, V and VI municipal roads, and urging municipalities to exercise the posting authority “in ways that do not unreasonably infringe on the efficient movement of unprocessed natural resources.” It is a legislative urging, not a limit.
The back half of RSA 231:191 is where the commercial consequences sit, and it is drafted with unusual symmetry — duties on the hauler, and deadlines on the municipality. Paragraph IV creates the restoration obligation: a person who violates the posted limits “shall be required to restore such highways if the municipality has reason to believe that the highway damage or disturbance is attributable to vehicles or activities under such person’s control or responsibility.” The trigger is the town’s belief, not a finding, and the qualifier travels with it.
The same paragraph gives the hauler a disclosure right against that belief: “Upon request, the municipality shall provide such person with the municipality’s reasons, including any inspection reports.” Inspection reports are documents, and a request for them is the first thing to make when a restoration demand arrives.
Paragraph V forecloses a grandfathering defense and then grants a mandatory exemption in the same sentence. No vehicle or commercial enterprise served by it is exempt from the posted limits because of prior highway use or existing use of abutting land — but any landowner or served commercial enterprise “who demonstrates that such limits would entail practical difficulty or unnecessary hardship, and who complies with all conditions and regulations concerning bonding and restoration, shall be granted an exemption unless the exemption would be detrimental to public safety.” The statute then defines the standard downward: unnecessary hardship “shall include any weight restriction which results in significant interference with a commercial enterprise or land use which existed prior to the posting of the weight restriction.”
That is a genuine remedy rather than an invitation to negotiate. An operation that predates the posting, that can show significant interference, and that accepts the bonding and restoration conditions is entitled to the exemption unless public safety says otherwise — and the bonding condition is precisely the point at which an insurance and surety conversation becomes part of a routing problem.
Paragraph VI attaches the penalty and the money. A person who violates any provision of the section or the rules made under it “shall be guilty of a violation if a natural person, or guilty of a misdemeanor if any other person; and in addition, shall be liable for the cost of restoration of the highway to a condition satisfactory to the person empowered to give such written permission.” A corporate operator takes the higher classification, and the restoration liability is measured by the satisfaction of the same official who grants permission under paragraph III.
Paragraph VII runs the other way and is the only calendar figure anywhere in the regime. Where a municipality establishes limits more restrictive than RSA 266:17-26 on a Class IV, V or VI highway, seasonal or otherwise, which restricts a commercial or industrial company operated or located in that municipality, it “shall hold a hearing if requested by the impacted business.” The hearing must be held within 15 working days of the local governing body’s receipt of a certified letter requesting it, “otherwise enforcement of the maximum weight limits established by that municipality shall be suspended for the remainder of the year or until such hearing is held.” The remedy for missing the deadline is automatic suspension of enforcement, and the trigger is a certified letter.
RSA 266:72, II names the aggregate commodity set in the statute itself. After a general requirement that any load and any covering on it be securely fastened against becoming loose, detached or a hazard to other users of the way, the paragraph continues: “Without limiting the foregoing provision, no person shall drive on any way any open vehicle loaded with earth, sand, asphalt, stone, gravel, or other particulate substance unless said vehicle is equipped with and said load is entirely covered and secured by a tarpaulin or similar covering which prevents the escape of any substance from said load onto the way.”
Three separate things must be true. The vehicle must be equipped with the covering. The load must be entirely covered. And the covering must be secured. A tarp rolled on a bad arm, or covering four-fifths of a heaped body, fails a different element than an untarped load does, and each is independently enforceable.
Paragraph I sits beneath it as the general escape prohibition — no vehicle may be driven unless so constructed or loaded as to prevent any of its load from dropping, sifting, leaking or otherwise escaping — with a narrow carve-out permitting sand to be dropped for the purpose of securing traction and water or other substance to be sprinkled on a way in cleaning or maintaining it.
The exemption at paragraph V is the part most often stated too broadly, and its internal condition changes its scope. Paragraphs II and II-a do not apply to “the operation of construction equipment as defined in RSA 259:42 and motor vehicles used in the construction of highways” — but only “provided that such equipment or motor vehicle is used within a highway construction zone as prescribed by the commissioner of transportation,” and with the driver expressly not relieved of the duty to exercise reasonable care. Outside the zone, a highway construction truck is under the tarp mandate like anyone else. Subparagraphs (b) and (c) add exemptions for municipal and state highway maintenance equipment, and for driving on a way at speeds of less than 30 miles per hour.
Paragraph III carries the penalty and the damage liability together: a violation if a natural person, a misdemeanor if any other person, and “Any person shall be liable to the state or town for any damage done to the way by spillage.” Paragraph IV exempts a local farmer transporting the farmer’s own farm products or materials incidental to a local farming operation, without relieving that farmer of the duty to exercise reasonable care to prevent hazardous spillage.
Material leaving a body is therefore three exposures at once in New Hampshire — a misdemeanor for the company, a statutory debt to the state or the town for the damage, and whatever the escaping material did to the vehicle behind. The last of those is an ordinary auto liability claim; the first two are not, and they attach to the entity rather than to the driver.
RSA 266:20 is short and unusually generous, and the generosity is in its final sentence. The section provides that RSA 266:18 shall not prohibit the driving of construction equipment and motor vehicles used in the construction or maintenance of highways, “provided that such equipment is used within a highway construction zone or extensions thereof as prescribed by the commissioner of the department of transportation.” Then: “The provisions of this section shall apply equally to all vehicles used for transporting distributable loads of construction materials within such zones.”
That last sentence is the one that reaches a dump operator. The exception is not confined to plant and machinery; it extends to vehicles hauling distributable loads of construction materials — which is what a dump body carries — so long as the movement stays inside a zone or its extensions.
The boundary of that zone is an administrative determination rather than a statutory distance. It is prescribed by the commissioner of the department of transportation, which means the operative question on a given job is what the department prescribed for that project, and where its extensions run. Two contractors on adjacent contracts can be working under different zone boundaries.
Bridge access is not relieved by any of this. RSA 266:18-c, IV prohibits driving or moving a vehicle or combination over any bridge or other structure on any way where the weight of the vehicle and load “is greater than the capacity of the structure as shown by a sign on the right side of or overhead on the structure.” Paragraph V places the duty to sign state-jurisdiction bridges on the commissioner of transportation and provides that “For all other bridges or other structures it shall be the duty of the authority having jurisdiction to place similar signs,” prescribing the sign copy — WEIGHT LIMIT X TONS — and an alternative percentage form, GROSS WEIGHT LIMIT X TONS OR Y% OF LEGAL LOADS, for structures that can safely carry more from vehicles with three or more axles.
The commissioner may alternatively post standardized warning signs designating certain restricted bridges as caution crossing bridges or as excluded bridges, and publish a list designating all such bridges “at least annually.” A New Hampshire route survey therefore has two independent inputs — what the town posted on the road, and what the authority having jurisdiction posted on the structure — and neither is derivable from the other.
Where a load will not fit inside any of the three schedules, the instrument is a special permit from the commissioner of transportation. RSA 266:24, I lets a person wishing to move an object or a vehicle and load exceeding the chapter’s weight, width, height or length — or whose load cannot be so distributed as to meet the chapter’s requirements — apply for a permit to move it upon a way, granted “upon a specified way and at a specified time” if in the commissioner’s opinion it will not be detrimental to the preservation of the way and the public use of it.
Two conditions in the same paragraph are worth knowing before an application goes in. The applicant, “if required by said commissioner and director, shall file a bond to cover any possible damage to the ways or to the bridges over which the object or vehicle and load to be moved may pass.” And the commissioner or the director of the division “may require a hearing before granting said permit.” Both are discretionary rather than standing, which is why they are easy to miss until they are asked for.
The section also declines to displace local authority. It “shall not be construed to limit the powers of the commissioner of transportation, selectmen of towns and city council of cities to make rules for the protection and to prevent the abuse of ways and bridges as provided by RSA 236:1, RSA 47:17 and RSA 41:11.” A state permit is not a municipal permission, and the posted-road regime above continues to run underneath it. Violating the conditions of a permit issued under the section is itself a violation.
The fees are set at RSA 266:22, which the commissioner collects before any RSA 266:24 permit issues, and which was last amended effective July 1, 2023. An over-length, over-width or over-height permit, or any combination of them, is $6. The overweight fee runs on a graduated schedule: $5.50 for vehicle and load over registered weight but not exceeding 50,000 pounds, then $6.50, $7.50, $8.50, $9.50 and $10.50 across successive 10,000-pound bands up to 100,000 pounds, “and for each additional 10,000 pounds $2 shall be added to the above rate.”
Two of the fee classes are structural rather than per-move, and they are the ones a working fleet uses. Paragraph III authorizes a permit covering “all types of moves made within a radius of 100 miles from the person’s home location for a fee of $60 for each unit,” issued for such time as the commissioner may determine. Paragraph IV authorizes “a special annual permit … to cover all types of moves for a fee of $115 for each unit,” issued for one year. Neither is commodity-limited on the face of the section — both cover all types of moves — and all permit revenue is credited to a nonlapsing revolving fund continually appropriated for the operation of the department’s permit section under paragraph VI.
One regional instrument exists and its scope should not be overstated. RSA 266:24-b authorizes the commissioner to enter “a multi-jurisdictional regional truck permit compact, to be known as the New England truck permit agreement, for oversize non-divisible interstate loads,” with rules that shall have the effect of law and that provide for member states to collect fees and perform audits on each other’s behalf. It is confined by its own terms to non-divisible loads, so a loaded aggregate body does not reach it. For the moves that do — a machine on a lowbed to a pit — an oversize and overweight program and the discretionary RSA 266:24 bond belong in the same conversation, alongside the general liability exposure that sits on the pit and stockpile work at either end.
The state minimum is a licensing threshold. The program an operator actually needs is built from these lines:
We write dump and aggregate hauling as a named class rather than as an exception to general trucking, and we read each account against the weight and permit regime of the state it operates in. For a New Hampshire operator that means starting from what the trucks are actually licensed and configured to carry, sizing physical damage to bodies and hoists rather than to a chassis value, and treating pit, stockpile and job-site work as its own exposure rather than an extension of the highway auto form.
If the operation also runs freight under separate authority, the New Hampshire trucking insurance page covers the state’s broader motor carrier picture, and the dump trucking insurance page covers the class mechanics that apply wherever the operator runs.
Because it splits the question by surface and by certification rather than answering it once. RSA 266:18 governs the interstate and defense highway system, RSA 266:18-a governs all other ways in the state, and RSA 266:18-b governs vehicles certified under RSA 266:18-d and only off the interstate. A single unit three-axle vehicle is capped at 47,500 pounds under the first, 55,000 under the second and 65,000 under the third — the same truck, three lawful gross weights.
It can be. RSA 266:18-a, II(b) allows a single unit three-axle vehicle 55,000 pounds on ways other than the interstate and defense highway system, while RSA 266:18, II(b) allows 47,500 pounds on that system. New Hampshire’s interstate mileage is the restrictive surface for this configuration, which reverses the assumption operators bring from many other states.
The instrument that unlocks the RSA 266:18-b schedule. RSA 266:18-d, I requires certification from the commissioner of the department of safety before a vehicle may exceed the RSA 266:18-a limits, and paragraph II sets an additional fee of $105 for a one-year term, covering a power unit and not more than one trailer. It expires on the sale or transfer of the vehicle, and it also becomes inoperative under paragraph V-b if the vehicle is placed out of service for a safety violation or cited for an axle distance violation.
Manufacturer attestation. RSA 266:18-d, III requires documentation satisfactory to the department, from the manufacturer, attesting that the vehicle can safely carry the additional weight, and designating the maximum safe gross weight “as determined by the components and the summation of the manufacturer’s axle design limits for each axle of the vehicle.” A new attestation is required whenever the configuration relative to power unit, axles, springs or other safety items affecting qualification is altered.
Yes, and it is in the statute rather than in practice. RSA 266:18-a directs that any police officer “shall allow on any way other than the interstate and defense highway system a tolerance of 5 percent above said limitations.” For a vehicle certified under RSA 266:18-d, RSA 266:18-b widens it to 5 percent above the limitations and 10 percent above the limitations on the axle weights.
On Class IV, V and VI highways, yes. RSA 231:191, I lets the governing body of a municipality set maximum weight limits, seasonal or otherwise, more restrictive than RSA 266:17-26 on those classes where the highway agent determines posting is needed to prevent unreasonable damage or extraordinary municipal maintenance expense. The limits bind only where posted at all entrances from other public highways, and written permission to exceed them comes from the selectmen or highway agent, or the mayor and aldermen or street commissioner.
There is a mandatory exemption if the showing is made. Under RSA 231:191, V a landowner or served commercial enterprise who demonstrates practical difficulty or unnecessary hardship, and who complies with all conditions and regulations concerning bonding and restoration, “shall be granted an exemption unless the exemption would be detrimental to public safety.” The paragraph defines unnecessary hardship to include any weight restriction causing significant interference with a commercial enterprise or land use that existed before the posting.
Enforcement stops. RSA 231:191, VII requires a municipality that has restricted a commercial or industrial company operated or located there to hold a hearing if the impacted business requests one, within 15 working days of the local governing body receiving a certified letter — “otherwise enforcement of the maximum weight limits established by that municipality shall be suspended for the remainder of the year or until such hearing is held.” The certified letter is what starts the clock.
Yes, by name. RSA 266:72, II prohibits driving any open vehicle loaded with earth, sand, asphalt, stone, gravel or other particulate substance unless the vehicle is equipped with, and the load entirely covered and secured by, a tarpaulin or similar covering preventing escape onto the way. The construction carve-out at paragraph V(a) is narrower than it reads: it applies only where the construction equipment or highway construction vehicle is used within a highway construction zone prescribed by the commissioner of transportation.
RSA 266:22 charges $6 for an over-length, over-width or over-height permit and runs overweight on a graduated schedule from $5.50 for vehicle and load over registered weight but not exceeding 50,000 pounds up to $10.50 in the 90,001 to 100,000 pound band, adding $2 for each additional 10,000 pounds. A radius permit covering all types of moves within 100 miles of the home location is $60 per unit, and a special annual permit covering all types of moves is $115 per unit. The section was last amended effective July 1, 2023.
Every figure on this page was read at the source below on August 11, 2026, with the effective date of the version read. Treat each as current as of that date rather than as permanent.
Send the declared or registered weights alongside the axle configurations, and tell us where the material moves from. We will size the program against the work the trucks actually do rather than against a statutory floor.
