BALTIMORE (AP) — A federal review has narrowed the possible routes for a proposed high-speed, magnetic levitation train linking Baltimore and Washington down to two.

Both routes more or less track the Baltimore-Washington Parkway. A route that would have run along the heavily developed Penn Line operated by Amtrak has been dropped.

The proposal calls for using maglev technology on a 40-mile, $10 billion line where trains could reach 375 mph, reducing the trip between the two cities to 15 minutes. Most of the route would be underground. Some communities along the proposed paths are opposed.

Northeast MAGLEV CEO Wayne Rogers said if the project continues to move forward as planned and the state gives the green light to a route, construction could begin in late 2020.

WTOP’s Mike Murillo contributed to this report.