The governor of Michigan signed a legislative package Friday that allows cars without steering wheels or drivers to be tested on the state's highways.
The plan is to make the state "the epicenter for driverless vehicle technology," said Gov. Rick Snyder.
Florida already allows testing of completely driverless cars. With the new law, Michigan and Florida now are the most liberal states on laws governing driverless car technology.
The bills drew strong bipartisan support as Michigan, the home of the U.S. auto industry, attempts to establish itself as a leader in driverless technology.
Most driverless car development to date, however, has been conducted outside Detroit, mostly in Silicon Valley and Pittsburgh.
In California, though, a human is required to be aboard driverless cars for vehicle testing, and the vehicle must be equipped with a steering wheel and brake pedals. The California Department of Motor Vehicles is considering changes to driverless car rules.
Lobbyists from Google and other companies with a stake in driverless car development are pushing California to ease up on current regulations.
The new Michigan laws will also allow testing of driverless car ride-hailing services, and permit truck platooning.
In platooning, big rigs use automated driving technology to follow each other closely enough to ride in the draft of the vehicle in front of it, saving fuel. A human driver ready to take control will be required in each truck.
The National Highway Traffic Safety Administration issued federal safety guidelines in September for testing of driverless cars. While the agency left it to states to decide what to allow on their highways, it urged the states to coordinate their regulations to avoid a patchwork of rules that could hinder driverless car development. The federal agency believes that automated vehicles hold the potential to significantly reduce traffic injuries and deaths.