Overview: Baltimore’s B&P Tunnels are some of the oldest structural assets on the Corridor and a major capacity bottleneck for both passenger and freight trains. The tunnels were constructed in 1873 – just eight years after the end of the Civil War. A series of three narrow profile tunnels in a more than one-mile stretch, they were originally constructed out of brick and stone masonry, though repairs through the years have introduced additional building materials. With just two tracks, the B&P Tunnels west of Baltimore Penn Station and the Union Tunnel to the east force the NEC to constrict down from four tracks as it passes through downtown Baltimore. Due to its tight curvature and aged structural conditions, the tunnel limits train speeds to 30 mph – down from 60 mph or higher on its approach tracks – and due to its height, the tunnel precludes the use of double-stack freight cars. The B&P Tunnels underwent rehabilitation in the 1980s, but that effort was not intended to be a permanent fix and the tunnels continue to require ongoing maintenance. High saturation of water in the soil beneath the tunnels, for example, causes its aging floor slabs to sink, forcing Amtrak to repeatedly make repairs.
In 2010, Maryland was awarded a $60 million HSIPR grant to complete preliminary engineering and environmental review of options to augment or replace the B&P Tunnels. While the alignment and design of any new tunnel is yet to be determined, planning will consider options for supporting higher-speed train service and creating separate routes for passenger and freight trains through Baltimore. New tunnels could free the existing tunnels for renewal, ultimately for additional capacity, and make Amtrak and MARC less susceptible to maintenance-related delays.