Will state-by-state regulation of self-driving vehicles work -- and keep people safe?

A future where motorists share streets and highways with driverless cars may still be years away, but transportation experts are saying now's the time for elected leaders to plan for that scenario.

Pennsylvania is the latest state to test drive the idea.

The state's Senate Transportation Committee approved a non-partisan bill on Jan. 26 that would expand regulatory rules concerning the operation and testing of highly automated vehicles, aka HAVs, and allow them to operate without anyone inside.

Legislators could vote on the bill later this year -- if approved, it would go into effect 90 days.

Transportation policy experts told ABC News that while there's clearly a need to create legal guardrails before the vehicles become commonplace, a unified national framework would be most efficient.

Bryan Reimer, director of MIT's Advanced Vehicle Technology Consortium, told ABC News that while state actions are good in the short term, it's more important if they can spur a bigger movement.

"It is clear we need to create a responsible disclosure when things happen with automated vehicles," he told ABC News. "There needs to be a discussion."

The Pennsylvania Lawmakers who sponsored SB 965 have said that they created it to boost their state's HAV industry, which includes a self-driving test lab at Carnegie Mellon University in Pittsburgh and eight private companies.

Under current Pennsylvania law, a human must be in the driver seat of an autonomous vehicle while it's in operation. The new bill removes that requirement.

Some states, such as Texas, Florida and Georgia, already allow HAVs to be operated without a human inside as long as the vehicle is registered with the state.

Pennsylvania State Sen. Wayne Langerholc Jr., SB 965's lead sponsor, told reporters at a Jan. 5 news conference that companies are heading to other states with more lenient rules on driverless vehicles.

"We dare to stay ahead of the curve," Langerholc said.

Similar to laws in other states, Pennsylvania's proposal would require vehicle owners to register within the state and remain at the scene of any accident involving another vehicle or a pedestrian.

Vehicle owners also must "submit proof of financial responsibility to the department self-certifying that the highly automated vehicle is covered by insurance or proof of self-insurance in an amount not to exceed $5 million," according to the bill's current language.

Pennsylvania Secretary of Transportation Yassmin Gramian, a supporter of the bill, said the autonomous vehicle industry already has generated 6,300 jobs for the state -- and SB 965 becoming law would mean adding even more.

The bill has the support of several groups, including the Greater Pittsburgh Chamber of Commerce.

"There's added economic benefit that will be created and produced for many years," Gramian said during the Jan. 5 news conference. "We cannot wait and become reactive anymore. The industry is moving very fast."

While the bill has broad support from legislators, one Pennsylvania-based transportation researcher told ABC News that leaders haven't covered all of their bases.

Philip Koopman, a professor at Carnegie Mellon University, warned lawmakers in an op-ed in the Pittsburgh Post-Gazette that the bill's current language lacks specific guidance in several areas.

Specifically, Koopman told ABC News, the bill lacks details on the potential legal liabilities of HAV companies linked to incidents, particularly if said vehicle doesn't have a single owner or operator.

The current bill "is filled with ambiguities," Koopman added. "If an ordinary citizen gets hurt, or possibly killed, it's unclear who to get compensation from."

MIT's Reimer also said the bill doesn't address the training that local law enforcement will need to properly regulate HAVs and investigate incidents. The National Transportation Safety Board currently investigates all crashes involving self-driving vehicles.

"I would argue states generally don't have the technical expertise to regulate a feature set that falls predominantly under federal regulations," he added. "It's not just about waiting for police response. They need to get the data from the companies and look at software."

Koopman also noted that, according to its current language, the bill would supersede any local regulation on autonomous vehicles, such as those put in place by former Pittsburgh Mayor William Peduto that stipulated companies must issue constant reports about self-driving field tests.

"One of the things is," Koopman continued, "we have a system that is working fairly working well now."

Koopman, who worked for the U.S. Department of Transportation and is a member of a committee that developed autonomous vehicle safety standards for the Society of Automotive Engineers International, said he's reached out to state lawmakers to get more clarification on the bill's safety measures.

Although Langerholc said the bill would incorporate the SAEI standards, Koopman noted that the bill's current language does not.

"If they want to use public roads as a laboratory, they need to provide something in return and lay out the rules now," Koopman said. "Otherwise we're going to head to more court battles."

As of Friday, Koopman said none of the bill's sponsors has returned his request to speak. Langerholc's office didn't immediately respond to requests for comment from ABC News.

The transportation experts said that as more states begin considering their own HAV-related regulations in the coming years, the best solution still would be federal guidelines to protect both people and commerce.

"It is a failure of national policy," Reimer said, "that states are creating this patchwork system."