Trip Permits are (generally) short term special use authorizations for a truck to operate with a state it does not normally operate within or hauling an unusually large or heavy load, even in the base state the truck is licensed in.
Many trucking companies do not pay the registration fees for all their trucks to be operated in all states. They many only establish authority to operate their trucks in a hand-full of states where they do most of their business. However, occasionally they need to send one or more rigs to other states to deliver or pickup cargo. TO legally enter a state and travel it’s highways, it is necessary for the company to obtain a Trip Permit. This can be done several ways. The company can contact the state directly and complete the process or the company can use a 3rd party commercial truck permit service. [If you google.com or bing.com Trip Permits, you will get dozens of companies that provide these services.]
The states, for the most part of made the process easy because it is all about revenue collection. To get the permit, you pay money. Now there are exceptions to the easy to do policy. Some states are much friendlier to work with then others. Names will not be named. That is one reason many companies will just turn to a commercial permitting company. Since these companies do this all day long and many have agents on duty 24/7, the extra cost of using them is offset by their ability to navigate the processes for each state and get it right the first time. A permit with errors could result in major fines and problems, including the truck and cargo being seized, until the issues are resolved.
Another common Trip Permit situation involves the moving of large or heavy loads. Loads exceeding 80,000 lbs generally must have special use permits. Key exceptions are that in some states, such as Michigan, truck/trailer combinations may have extra axles and thus authorized proportionately large loads. However, these trucks are restricted to in-state only and also pay substantially higher registration fees in the first place. Regardless of obtaining a trip permit, a truck is not allowed to haul heavier loads without more axles/wheels so it is not a simple matter to get an over weight permit and then put more on your standard 5 axle/18 wheeler.
Special Use Trip Permits may be required for wide and/or tall loads. As a part of the permitting process, the state(s) will identify the routes the load is authorized to take, the hours when the load can be moved (generally not at night) and special equipment/banners/markers that must be attached to the load. Additionally, the trucking company may be required to hire ‘Escorts’ to either precede the load, follow the load or both. Extra ordinarily large loads may have a police escort leading the procession, two private escort cars in front of the load and one of them with a height pole to check for anything not high enough to allow the load to pass under, and then a following escort car to warn drivers coming up from the rear an attempting to pass the load. All these requirements will be noted and specified in the trip permit or authorizations.
In the modern day of computers and online services and the use of the IFTA and IRP, trip permits are not as big an issue as they use to, however, a career truck driver will likely encounter a situation where they will need to deal with them.