WASHINGTON (Reuters) - In closed-door meetings last March, U.S. transportation regulators and others grappled with questions about whether police should have the power to disable self-driving cars and whether an automatic alert that a robo-taxi had been in a wreck could violate an occupant’s privacy, a report released on Tuesday showed.

The 39-page-summary of the meetings involving U.S. Transportation Department officials and industry, labor, and advocacy groups illustrated the thicket of legal, safety and social issues that have to be worked out as companies such as Alphabet Inc’s Waymo unit and General Motors Co gear up to deploy self-driving cars for public use.

Many participants in the meetings “agreed that it is a question of when, not if, there is a massive cyber security attack targeting” autonomous vehicles and said “planning exercises are needed to prepare for and mitigate a large-scale, potentially multimodal cyber security attack,” according to the report.

Law enforcement officials expressed interest in being able to interact with, direct, and potentially control AVs during emergencies, the report said.

However, the same pathways that would allow police to stop a self-driving car could be exploited by hackers or terrorists, the meeting participants said.

“At the end of the day, policymakers likely need to answer 10 to 15 key questions,” Derek Kan, the Transportation Department’s undersecretary for policy, said in March, according to the summary.

“These range from things like, how do you integrate with public safety officials? Should we require the exchange of data? What are our requirements around privacy or cyber security? And how do we address concerns from the disability and elderly communities?”

U.S. Transportation Secretary Elaine Chao said in San Francisco on Tuesday that “one thing is certain — the autonomous revolution is coming. And as government regulators, it is our responsibility to understand it and help prepare for it.”

She said “experts believe AVs can self-report crashes and provide data that could improve response to emergency situations.”

One issue is if self-driving vehicles should be required to be accessible to all disabled individuals, including the blind, the report noted.

The Transportation Department is expected to release updated autonomous vehicle guidance later this summer that could address some of the issues raised during the meetings.

Automakers, Waymo, a unit of Alphabet Inc, and other participants in the nascent autonomous vehicle industry have called for federal rules to avoid a patchwork of state regulation. However, the process of developing a federal legal framework for such vehicles is slow moving.

Chao said that after a crash in March involving an autonomous Uber [UBER.UL] vehicle in Tempe, Arizona, killed a woman who had been walking with her bike “public concern over autonomous vehicle technology spiked.”

In January, General Motors filed a petition seeking Transportation Department approval to deploy a fully autonomous car, one without a steering wheel or pedals, in a ride-sharing fleet in 2019.

The department has been reviewing GM’s petition for nearly six months and has not deemed it “complete,” a step before it would release proposal details and make a decision on the application.

In Congress, legislation to make it easier for automakers to get thousands of cars on the road without human controls is stalled and its prospects for approval are uncertain.