Whether you have to stop at a weigh station is set by the state you are driving in, not by one federal rule. In general, commercial trucks must pull in when the station is open and the signs say so, and the weight or vehicle type that triggers the stop varies by state. Federal law requires every state to enforce truck size and weight limits and to certify that it does; how each state does it, including who must stop, is in its own vehicle code.
Why weigh stations exist: the federal part
The federal rules do not tell drivers when to stop. They tell states to enforce. 23 CFR 657.5 states FHWA policy that "each State enforce vehicle size and weight laws to assure that violations are discouraged and that vehicles traversing the highway system do not exceed the limits specified by law," to protect pavement and bridges and keep the roads safe. Under 657.9 each state files an enforcement plan, and no plan is approved unless it uses at least two of four kinds of equipment: fixed platform scales, portable wheel weighers, semiportable or ramp scales, and weigh-in-motion (WIM) equipment. The plan also covers hours of operation "in general terms," policy on off-loading overweight divisible loads, penalties, and overweight permits.
Each year, under 657.13 and 657.15, the governor or a designee certifies that the state is enforcing its size and weight laws, and reports how many vehicles were weighed on fixed, semiportable, portable and WIM scales, how many citations were issued for axle, gross and bridge formula violations, how many loads were shifted or off-loaded, and how many overweight permits were issued. Under 657.19, a state that fails to certify or to enforce adequately can lose 10 percent of certain federal highway funds. That is the reason every state runs scales.
The limits being enforced on the Interstate are federal: 80,000 pounds gross, 20,000 on a single axle, 34,000 on a tandem, and the bridge formula (23 CFR 658.17). They are covered on the truck weight limits page.
Who has to stop: state law
Because stopping rules are state law, the only safe statement is what a given state’s code says. Two examples from official state sources:
California
California Vehicle Code 2813: "Every driver of a commercial vehicle shall stop and submit the vehicle to an inspection of the vehicle’s size, weight, equipment, loading, and smoke emissions, as well as the driver’s license, medical qualifications, and hours-of-service compliance of a driver of the vehicle at any location where members of the California Highway Patrol are conducting tests and inspections of commercial vehicles and when signs are displayed requiring the stop." Failing or refusing to stop when signs require it is a misdemeanor.
What counts as a "commercial vehicle" there is set by Vehicle Code 260: a motor vehicle of a type required to be registered "used or maintained for the transportation of persons for hire, compensation, or profit or designed, used, or maintained primarily for the transportation of property." Passenger vehicles and house cars not used for hire are not commercial vehicles. Note what is missing: a weight threshold. In California the test is use and design, which is why a pickup or van used to carry property for a business can be required to stop there, while a motorhome used privately is not.
Florida
Florida Statutes 316.545(1) authorizes any Florida Highway Patrol officer "having reason to believe that the weight of a vehicle and load is unlawful" to require the driver "to stop and submit to a weighing" on portable or fixed scales. Refusing is obstruction and a first-degree misdemeanor. Under 316.545(2)(a), if the weight is unlawful the officer may hold the vehicle until the penalty is determined, and any gross weight more than 6,000 pounds over the maximum must be unloaded.
Other states write their own triggers, which can turn on weight rating, registration class or the vehicle’s use. We have not verified each state’s rule, so we do not list thresholds here. The rule for any particular trip is: check the vehicle code or the highway patrol’s commercial enforcement page for each state on the route, and when in doubt, follow the signs.
Do pickups and RVs have to stop?
It depends on the state’s definition, and the two examples above show how different they are. In California a pickup used primarily to haul property for a business fits the Vehicle Code 260 definition and must stop when signs require it, while a privately used house car does not. In Florida the power is to stop any vehicle an officer has reason to believe is overweight. A personal pickup with no trailer is outside most states’ weigh station rules; a pickup towing a heavy trailer for a business, the hotshot setup, is often inside them. Look at your state’s definition, not at what other drivers do.
Open, closed and the signs
States decide their own hours, and 23 CFR 657.9 only asks for them "in general terms" in the enforcement plan. So there is no national schedule, and the weigh station data states publish, which our weigh station directory is built from, does not say whether a station is open now. The practical rule is the one in California’s code: the obligation is tied to signs being displayed. An "open" sign or flashing lights on the approach mean pull in; a "closed" sign means continue.
Bypass: PrePass, Drivewyze and the like
Bypass services are private systems that states let screen trucks electronically as they approach. PrePass describes its app as giving qualifying carriers "weigh station bypass message alerts that notify them to bypass, pull-in or follow road signs at PrePass-enabled weigh station sites." Drivewyze is another such service. The rules of bypass follow from that description:
- Only at enabled sites. A station that is not part of the program gives no signal, and the signs apply.
- Only for qualifying carriers. PrePass sends bypass messages to "qualifying carriers"; being enrolled does not mean every station will clear you.
- Pull-in means pull in. A bypass subscription is not an exemption. When the device says pull in, or says follow the signs, the signs govern.
- No signal is not a bypass. If the device does not respond, treat the station like any other.
The data a bypass screen checks overlaps with the CVSA Level VIII electronic inspection, which is done while the truck is moving and covers the driver’s identity, license, medical certificate, hours, registration, USDOT number, authority, UCR and federal out-of-service orders. See DOT inspection levels.
What happens inside
- Weigh-in-motion screening. Some stations weigh trucks as they roll over sensors on the approach. WIM equipment is named in 23 CFR 657.9 as one of the four kinds of equipment a state can use.
- The static scale. Trucks flagged by WIM, or all trucks where there is no WIM, roll across the platform scale axle by axle. A message board or light tells you to proceed or to park and bring in your paperwork.
- If overweight. What follows is state law: a citation or civil assessment, and in many cases shifting the load or off-loading. Florida, for example, requires any gross weight more than 6,000 pounds over the maximum to be unloaded (316.545(2)(a)). A driver can sometimes fix an axle overload by sliding the tandems or fifth wheel if the gross is legal; whether that is allowed on site is also state practice.
- Inspection. Many stations double as inspection sites. An officer may do a Level I, II or III inspection. California’s statute, for instance, lists equipment, loading, smoke emissions, license, medical qualifications and hours-of-service compliance among the things checked.
Scales away from the scale house
Weighing is not limited to fixed stations. Of the four kinds of equipment 23 CFR 657.9 lists, two are portable: portable wheel-load weighers and semiportable or ramp scales. Officers can set them up at the roadside, and the federal rules allow for their accuracy: under 23 CFR 658.17(g), a scale allowance of no more than 5 percent may be applied when portable wheel-load weighers are used, the only exception to the rule that the federal limits include all tolerances. The federal safety grant program also pays for this work: 49 CFR 350.227(b)(1) lets states be reimbursed for size and weight enforcement "at locations, other than fixed-weight facilities, where the weight of a CMV can significantly affect the safe operation of the vehicle, such as near steep grades or mountainous terrains, or at ports where intermodal shipping containers enter and leave the United States." Skipping a closed station does not mean the truck will not be weighed that day.
What to have ready at the window
If you are called in, the officer can ask for anything a Level III inspection covers. CVSA’s definition lists the driver’s license, the Medical Examiner’s Certificate and any Skill Performance Evaluation certificate, the record of duty status, hours-of-service compliance, the seat belt, vehicle inspection reports, and carrier identification and status. In practice that means:
- your license and your medical examiner’s certificate;
- your logs for today and the previous 7 days: 49 CFR 395.8(k)(2) requires a driver to have them available while on duty, and 395.13(b)(2) makes a missing record an out-of-service condition;
- on an ELD, the ability to transfer or display the records, and the in-cab ELD information packet required by 395.22(h);
- the registration, the shipping papers, and any oversize or overweight permit for the load.
Weigh stations and your hours
Time at a weigh station is on-duty time. The definition in 49 CFR 395.2 includes "all time in or on a commercial motor vehicle" other than resting, and "all time inspecting, servicing, or conditioning" a CMV. Time rolling across the scale is driving; time parked while an officer inspects the truck is on-duty not driving. It all runs on the 14-hour window, which is why a long inspection late in the day can leave a driver with less time to reach parking than planned. The HOS calculator shows what is left.
Worked example
Example, applying the California and federal rules above. A driver in a 5-axle tractor-trailer approaches a California scale with signs showing it open and a bypass device showing "pull in." Under Vehicle Code 2813 the driver must stop because signs are displayed and the vehicle is a commercial vehicle. On the scale, the drive tandem reads 35,200 pounds. On an Interstate route that exceeds the 34,000-pound tandem limit in 23 CFR 658.17(d), and under 658.17(g) federal Interstate limits include all enforcement tolerances. What happens next (a citation, sliding the tandems, or both) is the state’s decision.
Common mistakes
- "I’m under 26,001, so I never stop." Some states use lower thresholds or define commercial vehicles by use. Check the state.
- Treating a bypass subscription as permission. The device’s pull-in or follow-signs message governs.
- Relying on a cross-state tolerance. Some states apply a scale tolerance on their own roads, but on the Interstate the federal limits already include every tolerance except a portable scale allowance of no more than 5 percent (658.17(g)).
- Skipping an open station. In California it is a misdemeanor; other states set their own penalties.
Before you leave the yard
Weigh the load if you can, and check the axle groups against the limits with the bridge formula calculator. The weigh station directory lists stations and ports of entry by state and highway, with direction and mile marker where the state publishes them.