(Reuters) – The U.S. Transportation Department on Wednesday issued a draft environmental assessment for a Washington, D.C. to Baltimore tunnel that would carry passengers between the cities at high speeds in autonomous electric vehicles, the first step in a joint federal-state review of the Elon Musk project. Musk’s Boring Co has proposed a privately funded 35.3-mile “loop project” that would include twin underground tunnels transporting passengers at speeds of up to 150 miles per hour. The company says passengers would be able to travel from downtown Washington to Baltimore in as little as 15 minutes. Musk, who also leads electric vehicle maker Tesla Inc and rocket company SpaceX, is seeking to revolutionize transportation by digging tunnels, including one that would connect downtown Chicago and the city’s main airport. The draft assessment is an “early milestone in the environmental review and permitting process,” the Transportation Department said, adding it will be open for public comment for 45 days. Then the Federal Highway Administration and Maryland Department of Transportation will review comments and decide if a formal environmental impact statement is necessary. Final governmental approvals will depend on the outcome of the review and officials noted “operational safety issues will be addressed in future studies, as will the ultimate engineering and design details.” The tunnel route would largely follow the right-of-way under the Baltimore Washington Parkway and the proposed station terminals would be located on New York Avenue northwest of Washington’s Union Station and in the Camden Yards area in downtown Baltimore. The loop project is separate from hyperloop proposals, which involve ultra-high speed, fixed intercity transportation systems in which passengers are transported in pressurized capsules that operate in sealed partial-vacuum tubes at 600 miles per hour or faster, the department said. Boring says the loop tunnels would be compatible with hyperloop requirements and the loop tunnels could eventually be part of the faster system. The Transportation Department said tunnel activity will take place at an average of 30 feet below ground and the draft review addresses noise or vibration impacts at surface level, which according to the proposal are expected to be “minimal, subject to further design and engineering analysis.” Last year, Chicago selected Boring to build a $1 billion underground transit system to take people from Chicago’s downtown Loop district to O’Hare International Airport. The Chicago project’s fate is up in the air and Boring has yet to sign a contract with the city to build the tunnels. Boring did not immediately comment Wednesday but has said the East Coast tunnel “would serve as the central artery for a potential future transportation network which would hopefully be extended to New York.” Boring says it would take between 12 and 20 months to dig the tunnels and would include up to 70 ventilation shafts/emergency exits on private property adjacent to the alignment.