Truck weigh stations serve to calculate fuel tax and to enforce maximum weight restrictions on the highways. Sometimes safety inspections are done at weigh stations to confirm that the truck and driver are following other laws.
Several weigh stations now have "weigh-in-motion" technology where the truck is weighed on the highway approximately a mile before reaching the station. If the weight is close to the maximum or if the trucking company's history is questionable, the weigh station sends a message to the trucker to enter the station. The federal weight restriction is 80,000 pounds, although state maximums vary. Both the gross weight and the amount of weight carried by each axle are measured.
Once a truck enters the station, the truck's weight is measured on a fixed scale. If the truck is overweight, the inspectors can order the vehicle to stop until an overweight permit is awarded, fine the driver, or require the driver to remove the extra weight. The inspectors also have to power to check the trucker's paperwork and logbooks to ensure that fuel taxes and hours of service are honored. Furthermore, if an inspector notices a visible problem, such as a broken light or a fatigued driver, a thorough safety inspection is done before the truck can continue their route.