Baltimore and Potomac Tunnel

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West portal of B&P Tunnel in 1977.

The Baltimore and Potomac Tunnel (or B&P Tunnel) is a double track, masonry arch railroad tunnel on the Northeast Corridor in Baltimore, Maryland, immediately to the south of Pennsylvania Station. Approximately 140 Amtrak and MARC passenger trains, as well as two freight trains, use the tunnel daily.[1]

The 7,669-foot (2,338 m) tunnel facility, which passes under the Baltimore neighborhoods of Bolton Hill, Madison Park, and Upton, consists of a series of three tunnel sections—Gilmor Street Tunnel, Wilson Street Tunnel, and John Street Tunnel—delineated by two open air cuts—Pennsylvania Avenue Opening and John Street Opening.[1][2][3]

History and operations[edit]

Constructed by the Baltimore and Potomac Railroad under Winchester Street and Wilson Street in Baltimore, the tunnel opened on June 29, 1873.[4] The B&P tunnel allowed the Pennsylvania Railroad (PRR) direct access to Washington, D.C. for the first time by connecting its Northern Central Railway affiliate (which arrived in Baltimore from the north) to the Baltimore and Potomac's new spur, which ran to Washington.[5]

Between 1916 and 1917, the PRR lowered the floor of the tunnel approximately 2 12 feet to accommodate larger trains. The work included the underpinning of the side walls, installation of a concrete invert slab, and reconstruction of the track structure. The bases of the tunnel walls were chipped away to improve horizontal clearance.[6]

Prior to the electrification of the PRR's New York City to Washington main line in 1935, the poorly-ventilated tunnel easily filled with smoke from the steam locomotives then in use. The smoke also was a nuisance to the residential neighborhoods above the tunnel.[6]

The tunnel was lined with gunite to waterproof the arch and prevent icicles from shorting out the catenary wires prior to the initiation of electrified operation. However, financial considerations prevented the PRR from constructing a new passenger tunnel on the Presstman Street alignment, for which it previously had acquired rights. The PRR’s plan had envisioned using the new Presstman Street tunnel and the original bores of the Union Tunnel for passenger operations, while the old B&P Tunnel and the newer bores of the Union Tunnel (completed in the 1930s) would have been used for freight operations.[6]

In the late 1950s, the tunnel became a hindrance to the growth of PRR’s Trailer-on-Train service, which required additional vertical and horizontal clearance to accommodate semi-trailers on top of railroad flatcars. The curve at Pennsylvania Avenue was the biggest constraint. The PRR modified the tunnel walls and ceiling for a distance of 2,200 feet (670 m) to improve clearance and enable high cars and piggyback trailers to traverse the tunnel without damaging their roofs.[6] Additionally, a 928-foot (283 m) long gauntlet track was installed on southbound track 3 to route trains 17 inches (430 mm) closer to the middle of the tunnel. However, trains could not operate on track 2 while track 3 and the gauntlet were being used. The gauntlet track effectively created a single-track tunnel when in use; if a freight train broke down while using the gauntlet, the tunnel was closed to traffic until the train was moved.[6]

Even with the gauntlet, cars with a loading gauge in excess of Plate C or in excess of 16 feet 3 inches (4.95 m) high were prevented from using the tunnel.[6]

The tunnel underwent rehabilitation as part of the Northeast Corridor Improvement Project in the early 1980s. The repairs included replacing the existing invert, repairing the tunnel lining, upgrading the track structure, installing a new gauntlet track, and rehabilitating the tunnel drainage system. No fundamental change, however, was made in the tunnel’s difficult geometry. Eventually, the gauntlet track was removed due to changes in freight traffic patterns.[6]


The tunnel is a bottleneck for rail traffic along the Northeast Corridor and maintaining it is costly:

  • A sharp curve at the south portal of the tunnel prevents southbound trains from exceeding 30 mph (48 km/h) while in the tunnel[6]
  • The spacing between tracks is tight
  • There are water infiltration and drainage issues
  • An uphill, mile-long, 1.34 percent grade—the steepest grade on the NEC between Philadelphia and Washington—further constrains train performance.[6][7]

Collectively, the tunnel's height, speed, and capacity limitations threaten the ability for the Port of Baltimore to be competitive with increased shipping volumes.

Plans for improvements[edit]

In June 2008, the U.S. House of Representatives voted to support a study of the environmental impacts of different possible replacement tunnels.[1] On January 28, 2010, $60 million in funding was awarded under the American Recovery and Reinvestment Act to conduct the study, but not the money that will be required for a replacement tunnel.[8] Estimates in 2013 put the cost around $1.5 billion.[9]

An outgrowth of the ARRA funds, the B&P Tunnel Project is an environmental and engineering study by the FRA, MDOT, and Amtrak to evaluate potential improvements to the tunnel. The study has held multiple open houses in 2014–2015 to share information and solicit public input.

Preliminary Alternatives[edit]

In December 2014, the study published the Preliminary Alternatives Screening Report, in which four alternatives from a total of 16 were selected to be carried forward for further consideration and study:[10][11][12]

  • Alternative 1, No Build: do nothing
  • Alternative 2, Rebuild/Rehabilitate: improve the existing tunnel to either eliminate the need for a new tunnel or complement a new tunnel[3]
  • Alternative 3, Great Circle Passenger Tunnel: construct a new 10,900 feet (3,300 m) tunnel on a wide, continuous arc to the north of the existing tunnel, bypassing it entirely[13]
  • Alternative 11, Robert Street South: construct a new 9,500 feet (2,900 m) tunnel roughly parallel to and within 2–4 blocks of the existing tunnel[14]

Among the criteria used to evaluate the alternatives was the ability to accommodate double-stack container cars.[15]

The 12 eliminated alternatives included those with alignments that varied greatly from the existing alignment and bypassed Pennsylvania Station entirely, those that reused one or more of the three existing tunnel sections, and one that would have utilized the former I-170 "Highway to Nowhere" right of way.[12]

Final Alternatives[edit]

In October 2015, the study published the Alternatives Report, in which two of the preliminary alternatives—Alternative 2 (Rebuild/Rehabilitate) and Alternative 11 (Robert Street South)—were eliminated from further consideration due to concerns such as their greater impact and disruption to the community, greater disruption to existing train service (in the case of Alternative 2), and greater cost. The two remaining alternatives—Alternative 1 (No Build) and Alternative 3 (Great Circle)—will be carried forward, studied, and evaluated further in the next milestone, the Draft Environmental Impact Statement.[16][17]

See also[edit]


  1. ^ a b c Brown, Matthew Hay (2008-06-12). "House OKs funds for tunnel study: Alternative sought to outmoded passage that runs under city". The Baltimore Sun. 
  2. ^ "Existing B&P Tunnel and Vicinity Map" (PDF). B&P Tunnel Project. May 2014. 
  3. ^ a b "Alternative 2: Restore/Rehabilitate Existing Tunnel" (PDF). B&P Tunnel Project. October 2014. 
  4. ^ Wilson, William Bender (1895). History of the Pennsylvania Railroad Company: With Plan of Organization. Philadelphia: Henry T. Coates. p. 339. 
  5. ^ Robert T. Netzlof (2002-06-12). "Corporate Genealogy Union Railroad". Retrieved 2007-10-01. 
  6. ^ a b c d e f g h i U.S. Federal Railroad Administration. Washington, DC. "Report To Congress: Baltimore's Railroad Network, Challenges and Alternatives." November 2005. p. 2.16.
  7. ^ "Purpose and Need Statement" (PDF). B&P Tunnel Project. September 29, 2014. 
  8. ^ "Mikulski, Cardin Laud Federal Investment in High-Speed Rail for Maryland" (Press release). U.S. Senator Barbara Mikulski. 2010-01-28. 
  9. ^ Rector, Kevin (22 November 2013). "Aged tunnel where Amtrak train derailed may be replaced". The Baltimore Sun. Retrieved 25 November 2013. 
  10. ^ "Preliminary Alternatives Screening Report" (PDF). B&P Tunnel Project. December 2014. 
  11. ^ "Next Steps" (PDF). B&P Tunnel Project. October 2014. 
  12. ^ a b "Preliminary Alternatives Map" (PDF). B&P Tunnel Project. October 2014. 
  13. ^ "Alternative 3: Great Circle Passenger Tunnel" (PDF). B&P Tunnel Project. October 2014. 
  14. ^ "Alternative 11: Robert Street South" (PDF). B&P Tunnel Project. October 2014. 
  15. ^ "Evaluation of Preliminary Alternatives" (PDF). B&P Tunnel Project. October 2014. 
  16. ^ "Alternatives Evaluation Process" (PDF). B&P Tunnel Project. October 2015. 
  17. ^ "B&P Tunnel Project Update" (PDF). B&P Tunnel Project. October 2015. 

External links[edit]

  • U.S. Federal Railroad Administration. Report To Congress: Baltimore's Railroad Network, Challenges and Alternatives. November 2005.
  • B&P Tunnel Project

Coordinates: 39°18′11″N 76°38′07″W / 39.303°N 76.6352°W / 39.303; -76.6352