The proposed project will replace the 1.4-mile-long (2.25km) rail tunnel located along the Northeast Corridor (NEC) in Baltimore, Maryland. Built in 1873, the B&P Tunnel is one of the oldest structures on the NEC, and is nearing the end of its useful life. The existing double-track tunnel was constructed out of brick and stone masonry, with additional materials added over time.

The selected alternative (3B) is estimated to cost USD 4.5bn, and would include 2 miles (3.21km) of underground construction through variable ground conditions including soils, mixed face and rock. The alignment would travel through an existing retaining wall adjacent to an LRT rail station to begin its descent below ground. The Selected Alternative would continue below ground in a gradual arc traversing below primarily residential city before exiting via a south portal located southeast of the existing NEC tracks.

The B&P Tunnel is owned by Amtrak and used for Regional and Acela intercity passenger trains, Maryland Area Rail Commuter passenger trains, and Norfolk Southern Railway freight trains. The Maryland Department of Transportation (MDOT) issued a Draft Environmental Impact Statement in December, 2015 that evaluated the environmental impacts of three build alternatives, and the FRA and MDOT issued a Final Environmental Impact Statement on November 25, 2016.

Amtrak said on March 31 funding has not currently been identified for final design and construction of the project.