Why Do Some Semi-Trucks Have Multiple License Plates?

If you've ever watched Kris Kristofferson's 1978 movie "Convoy," you may have noticed that the semi-trucks making up the convoy sport multiple license plates. Similarly, in Steven Spielberg's 1971 film "Duel," the Peterbilt – one of the most popular semi-truck brands in America – has no less than six license plates, all from different states. Although Spielberg said in an interview that these were the driver's kill trophies, "the notches in his Colt 45," it could be that the homicidal truck driver was just a stickler for adhering to vehicle licensing regulations. 

Back in the 1970s, when these movies were made, truckers were required to register their vehicles separately in each state they operated. This meant obtaining license plates for every state a truck ran through, leading to some trucks displaying a variety of plates on their front bumpers. For instance, a truck operating along the West Coast might have needed separate plates for California, Oregon, and Washington. This patchwork of regulations made long-haul trucking a logistical challenge, with multiple registrations and associated paperwork being among the documents and information semi-truck drivers always need to have on hand. 

This system was time-consuming and expensive, as each state imposed its own registration fees and requirements. Everything changed with the introduction of the International Registration Plan, which simplified the process and meant that most truckers only needed to display one plate. However, there are some exceptions, which is why you still might see multiple plates on semi-trucks today.

In the 1970s, the trucking industry and state governments collaborated to create the International Registration Plan, which removed the need for multiple license plates on semi trucks. All 48 contiguous U.S. states and 10 Canadian provinces are members. The first states to enter the plan were Missouri, Tennessee, Kentucky, and Texas in 1974. Throughout the next decades, other states and provinces signed up. New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, and Quebec were the last to join, in April 2001.

The agreement facilitates the distribution of registration fees for commercial vehicles traveling across multiple jurisdictions. Under this plan, truckers can register their vehicles in a base state, and the fees are then apportioned based on the miles traveled in each member jurisdiction. The upshot of this is that semi-trucks now only require one plate that covers these 58 jurisdictions. You could theoretically have multiple plates if you were dual-registered in two member states, but this would be more expensive than having an apportioned plate.

However, some places in the U.S. and Canada remain outside the International Registration Plan. This includes Alaska and the three Canadian territories, Nunavut, Yukon, and Northwest Territories. (Hawaii is also outside the compact, but it's quite difficult to drive a truck there from any of the plan's jurisdictions, anyway.)

This means you can still see semi-trucks with multiple plates. Any trucker who regularly runs to Alaska or the Canadian territories from a plan jurisdiction might choose to register their vehicle separately in those places and get the appropriate plates. In many cases, there's also the option to purchase temporary permits rather than getting plates, so not every semi-truck you see in Yukon, for example, will have Yukon plates.

If you're wondering why you don't need to worry about any of this when you're driving your regular car from state to state, it's because this legislation only applies to vehicles transporting goods vehicles or passengers that weigh more than 26,000 pounds or have three or more axles. It's a tractor, bus and semi-truck thing (and here's what "semi" means on a semi-truck).