Gov. Rick Snyder today signed the long-called-for automated motor vehicle legislation, allowing for manufacturers to test driverless cars on Michigan roads.

The two bills, SB 169 and SB 663, passed the Michigan Senate earlier this month.

SB 169 allows automakers, suppliers and upfitters to test the technology on public roads, but regulations state that a human must be in the driver's seat during testing to intervene, if necessary.

SB 663, a companion bill, provides liability protection for automakers from civil suits caused by defective technology from suppliers.

Michigan joins California, Nevada, Florida and Washington, D.C., in passing driverless car legislation. Eight other states have been debating similar bills.

"Michigan is the automotive capital of the world," Snyder said in a statement. "By allowing the testing of automated, driverless cars today, we will stay at the forefront in automotive technological advances that will make driving safer and more efficient in the future."

Sen. Mike Kowall, R-White Lake, who introduced both bills, told Crain's earlier this year that they are less about legalization and more about promoting autonomous technology in Michigan.

"This is really a huge economic development bill," Kowall said. "This is going to have an effect of attracting new companies and building upon existing companies that are already here."

Kowall said the state laws will serve as a stand-in until the U.S. Department of Transportation and the National Highway Traffic Safety Administration weigh in on the federal level.

Auburn Hills-based Continental Automotive Inc. predicts partially automated vehicles will be market-ready by 2016, with combined technologies such as adaptive cruise control and accident avoidance systems. Adaptive cruise control uses forward-facing radar and camera systems to detect the speed and distance of the vehicle ahead of it — allowing a driver to simply follow the lead car when enabled.

Semi-automated vehicles, where the driver still must interact but not operate all functions of driving, will hit the market in 2020, the company has said.

By 2025, some cars may drive fully independently, experts are predicting.

Continental has logged thousands of hours on its semi-automated Volkswagen Passat in Michigan, Arizona and Nevada. It also helped draft the proposed changes to Michigan's Motor Vehicle Code.

Continental tests the Passat at its test tracks in Auburn Hills and Brimley, Mich., as well as on public roads around the state — always with a driver behind the wheel, the company said.

"The legislation is very important to us," said Steffen Linkenbach, director of systems and technology for Continental Automotive's chassis and safety division, in an interview with Crain's earlier this year. "Obviously, if you're looking at this from a macro level, Michigan is a place that's conducive to this type of testing; it already has the high-tech suppliers in this area."

Earlier this month, Ford Motor Co. joined the growing list of automakers working on driverless vehicle technology. It announced a partnership with the University of Michigan and State Farm Mutual Automobile Insurance Co. in the United States to test how the technology might be applied to reduce congestion and improve traffic safety.

Renault-Nissan CEO Carlos Ghosn said earlier this year that his company plans to have driverless cars available by 2020.