State and city officials stood in a the door of a new commuter-rail coach parked in the old Allston freight yard to announce a $25-million train station.
West Station will be built near the present turnpike toll plaza and should open when the turnpike there is straightened, in 2020, state Transportation Secretary Richard Davey said.
The station will be servced by DMUs, single-car diesel units that could bring subway-like schedules.
Davey said he hopes the new trains could eventually go to North Station via the Grand Junction bridge over the Charles, but acknowledged that will take considerable work, both to fix the tracks and convince skeptical Cambridge officials.
Gov. Patrick said if the Grand Junction could be put into service, that could one day lead to service from Allston to Assembly Row in Somerville.
Davey said Harvard, which owns the freight yard, agreed to kick in a third of the station's cost. The state will pay another third, with the source of the remainder to be determined.
Patrick and Mayor Walsh said Harvard has also agreed to make the streets in the new neighborhood that will spring up over the next two decades "multi-modal" - to safely carry pedestrians, bicyclists and motor vehicles.
Patrick, Davey and Walsh in the vestibule of the new commuter-rail car they used for the announcement: