<P> Many jurisdictions employ the use of portable scales, allowing weigh stations to be set up at any point . Portable scales allow states to set up temporary scales for situations such as seasonal check points, temporary checkpoints on isolated roads often used by trucks, and help prevent drivers from avoiding scales at fixed locations . Portable scales may be set up at purpose built locations that are not normally manned . A common reason for setting up portable scales is to monitor trucks during harvest season . </P> <P> A weigh station located near a state border is called a port of entry . States may also locate weigh stations in the interior of the state . Interior weigh stations are often located at choke points or areas where freight originates or is delivered . </P> <P> Weigh stations were primarily created to collect road use taxes before IFTA created an integrated system of doing so . While taxes can still be paid at weigh stations, their primary function is now enforcement of tax and safety regulations . These include: to check freight carrier compliance with fuel tax laws; to check weight restrictions; to check equipment safety; to check compliance with hours of service Regulations . Weigh stations are regulated by individual state governments and therefore have vastly different requirements from state to state . They are typically operated by the state's Department of Transportation (DOT) or Department of Motor Vehicles (DMV) in conjunction with the state highway patrol or state police, thus enabling enforcement of applicable laws . The federal maximum weight is set at 80,000 pounds . Trucks exceeding the federal weight limit can still operate on the country's highways with an overweight permit, but such permits are only issued before the scheduled trip and expire at the end of the trip . Overweight permits are only issued for loads that cannot be broken down to smaller shipments that fall below the federal weight limit, and if there is no other alternative to moving the cargo by truck . Permitted oversize trucks are often required to coordinate with the Departments of Transportation and law enforcement agencies of the transited states before the trip begins, as most states require oversize trucks to be escorted . Many states have weigh in motion technology that allow a continuous flow of truck weighing . </P> <P> Many states also check freight paperwork, vehicle paperwork, and logbooks to ensure that fuel taxes have been paid and that truck drivers are obeying the hours of service (a federal requirement). Also, the truck and driver may have to undergo a DOT inspection, as most states perform the bulk of their DOT inspections at their weigh stations . In some cases, if a truck is found to be overweight, the vehicle is ordered to stop until the situation can be fixed by acquiring an overweight permit . In other cases, the driver may receive an overweight ticket and may or may not be required to offload the extra freight . Offloading the extra freight may not be practical for perishable or hazardous loads . The first state to implement a weight law was Maine, which set a limit of 18,000 pounds (9 tons; 8,200 kg) in 1918 . </P>

When do you have to pull into a weigh station