WASHINGTON (Reuters) - U.S. Transportation Secretary Elaine Chao said on Thursday that regulators will seek public input on rules for self-driving commercial vehicles and trains, as the administration grapples with how to regulate their expected future use.

At a speech in Washington, Chao said the Federal Motor Carrier Safety Administration was asking for public comment on regulations that need revising or eliminating to “facilitate the safe introduction of automated technology on commercial motor vehicles” like large trucks.

In addition, the Federal Railroad Administration “is requesting information and comment on the future of automation in the railroad industry.”

Officials are also weighing how self-driving vehicles will impact ports and other transportation issues.

General Motors Co, Alphabet Inc, and many other companies are pursuing self-driving car technologies and want Congress and regulators to remove legal barriers to the vehicles.

Chao was talking at a summit on the topic held by the U.S. National Highway Traffic Safety Administration (NHTSA) on Thursday.

She said earlier this week that the administration of President Donald Trump would unveil revised self-driving car guidelines in August, as it sets out to rewrite the regulations.

The administration wants to clarify the federal versus state role, said Transportation Under Secretary Derek Kan, speaking on Thursday at the same event.

States currently regulate speed limits and driver behavior like alcohol consumption, while the federal government regulates vehicle performance. “What happens when the driver is now part of the machine?” Kan asked at the event.

Federal policymakers still must answer at least 10 key self-driving questions, Kan added, including on data, cybersecurity and privacy.

Bills in Congress to speed the introduction of self-driving cars do not include commercial trucks and have stalled recently over concerns they do not include enough safeguards.

In September, Chao announced the first set of revisions to guidelines set by the administration of former President Barack Obama.

Under existing rules, many written with the assumption that a licensed driver will be in control of the vehicle, automakers must meet nearly 75 safety standards. NHTSA said in 2016 that the regulations posed “significant” hurdles to vehicles without human controls.

The Federal Transit Administration recently sought public input on autonomous bus technology and regulatory barriers, while the Federal Highway Administration sought views on how U.S. roads must adapt to autonomous technology.

In January, GM filed a petition with NHTSA requesting an exemption for a small number of autonomous vehicles in a ride-share program without steering wheels or human drivers. The department has still not determined whether that petition is “complete” before deciding whether to approve it.