Baltimore and Potomac Tunnel
Encyclopedia
The Baltimore and Potomac Tunnel (or B&P Tunnel) is a double track
, masonry arch
railroad tunnel
beneath Baltimore, Maryland. It now serves Northeast Corridor
rail service operated by Amtrak
and MARC Train
passenger railroads with an average of 135 trains per weekday traversing the tunnel.
Whether considered a single 7669 feet (2,337.5 m) bore punctuated by two short open cuts, or thought of as a tunnel with three sections, the facility is collectively referred to as the B&P Tunnel and constitutes the southern approach to Pennsylvania Station
. It passes under the Baltimore neighborhoods of Bolton Hill, Madison Park and Upton, and is a bottleneck for rail traffic along the Northeast Corridor
. A sharp curve at the south portal of the tunnel prevents southbound trains from exceeding 30 mi/h while in the tunnel.U.S. Federal Railroad Administration. Washington, DC. "Report To Congress: Baltimore's Railroad Network, Challenges and Alternatives." November 2005. p. 2.16.
An uphill, mile-long, 1.34 percent grade further constrains train performance.
(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 main line, which ran to Washington.
Between 1916 and 1917, the PRR lowered the floor of the tunnel approximately 2½ 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.
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.
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.
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-trailer
s on top of railroad flatcar
s. The curve at Pennsylvania Avenue was the biggest constraint. The PRR modified the tunnel walls and ceiling for a distance of 2200 feet (670.6 m) to improve clearance and enable high cars and piggyback trailers to traverse the tunnel without damaging their roofs. Additionally, a 928 feet (282.9 m) long gantlet track
was installed on southbound track 3 to route trains 17 inches (431.8 mm) closer to the middle of the tunnel. However, trains could not operate on track 2 while track 3 and the gantlet were being used. The gantlet track effectively created a single-track tunnel when in use; if a freight train broke down while using the gantlet, the tunnel was closed to traffic until the train was moved.
Even with the gantlet, cars with a loading gauge
in excess of Plate C or in excess of 16 in 3 in (4.95 m) high were prevented from using the tunnel.
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 gantlet track, and rehabilitating the tunnel drainage system. No fundamental change, however, was made in the tunnel’s difficult geometry. Eventually, the gantlet track was removed due to changes in freight traffic patterns.
of different possible replacement tunnels. On January 28, 2010, $60 million in funding was awarded under the American Recovery and Reinvestment Act to conduct the study, but not the estimated billions of dollars that will be required for a replacement tunnel.
Double track
A double track railway usually involves running one track in each direction, compared to a single track railway where trains in both directions share the same track.- Overview :...
, masonry arch
Arch
An arch is a structure that spans a space and supports a load. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.-Technical aspects:The...
railroad tunnel
Tunnel
A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...
beneath Baltimore, Maryland. It now serves Northeast Corridor
Northeast Corridor
The Northeast Corridor is a fully electrified railway line owned primarily by Amtrak serving the Northeast megalopolis of the United States from Boston in the north, via New York to Washington, D.C. in the south, with branches serving other cities...
rail service operated by Amtrak
Amtrak
The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...
and MARC Train
MARC Train
MARC , known prior to 1984 as Maryland Rail Commuter Service, is a regional rail system comprising three lines in the Baltimore-Washington Metropolitan Area. MARC is administered by the Maryland Transit Administration , a Maryland Department of Transportation agency, and is operated under contract...
passenger railroads with an average of 135 trains per weekday traversing the tunnel.
Whether considered a single 7669 feet (2,337.5 m) bore punctuated by two short open cuts, or thought of as a tunnel with three sections, the facility is collectively referred to as the B&P Tunnel and constitutes the southern approach to Pennsylvania Station
Pennsylvania Station (Baltimore)
Pennsylvania Station is the main train station in Baltimore, Maryland. Designed by New York architect Kenneth MacKenzie Murchison , it was constructed in 1911 in the Beaux-Arts style of architecture for the Pennsylvania Railroad. It is located at 1515 N...
. It passes under the Baltimore neighborhoods of Bolton Hill, Madison Park and Upton, and is a bottleneck for rail traffic along the Northeast Corridor
Northeast Corridor
The Northeast Corridor is a fully electrified railway line owned primarily by Amtrak serving the Northeast megalopolis of the United States from Boston in the north, via New York to Washington, D.C. in the south, with branches serving other cities...
. A sharp curve at the south portal of the tunnel prevents southbound trains from exceeding 30 mi/h while in the tunnel.U.S. Federal Railroad Administration. Washington, DC. "Report To Congress: Baltimore's Railroad Network, Challenges and Alternatives." November 2005. p. 2.16.
An uphill, mile-long, 1.34 percent grade further constrains train performance.
Construction and Modifications
Constructed by the Baltimore and Potomac Railroad under Winchester Street and Wilson Street in Baltimore, the tunnel opened on June 29, 1873. The B&P tunnel allowed the Pennsylvania RailroadPennsylvania Railroad
The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....
(PRR) direct access to Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
for the first time by connecting its Northern Central Railway
Northern Central Railway
The Northern Central Railway was a Class I Railroad connecting Baltimore, Maryland with Sunbury, Pennsylvania. Completed in 1858, the line came under the control of the Pennsylvania Railroad in 1861, when the PRR acquired a controlling interest in the Northern Central's stock to compete with the...
affiliate (which arrived in Baltimore from the north) to the Baltimore and Potomac's new main line, which ran to Washington.
Between 1916 and 1917, the PRR lowered the floor of the tunnel approximately 2½ 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.
Prior to the electrification
Railroad electrification in the United States
Railroad electrification in the United States comprised many different systems in many different geographical areas, few of which were connected. Despite this, there were a small number of common reasons for electrification....
of the PRR's New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
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.
The tunnel was lined with gunite to waterproof the arch and prevent icicles from shorting out the catenary wires
Overhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
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.
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-trailer
Semi-trailer
A semi-trailer is a trailer without a front axle. A large proportion of its weight is supported by a road tractor, a detachable front axle assembly known as a dolly, or the tail of another trailer...
s on top of railroad flatcar
Flatcar
A flatcar is a piece of railroad or railway rolling stock that consists of an open, flat deck on four or six wheels or a pair of trucks or bogies . The deck of the car can be wood or steel, and the sides of the deck can include pockets for stakes or tie-down points to secure loads...
s. The curve at Pennsylvania Avenue was the biggest constraint. The PRR modified the tunnel walls and ceiling for a distance of 2200 feet (670.6 m) to improve clearance and enable high cars and piggyback trailers to traverse the tunnel without damaging their roofs. Additionally, a 928 feet (282.9 m) long gantlet track
Gantlet track
Gauntlet track or interlaced track is an arrangement in which railway tracks run parallel on a single track bed and are interlaced such that only one pair of rails may be used at a time. Since this requires only slightly more width than a single track, all four rails can be carried on the same...
was installed on southbound track 3 to route trains 17 inches (431.8 mm) closer to the middle of the tunnel. However, trains could not operate on track 2 while track 3 and the gantlet were being used. The gantlet track effectively created a single-track tunnel when in use; if a freight train broke down while using the gantlet, the tunnel was closed to traffic until the train was moved.
Even with the gantlet, cars with a loading gauge
Loading gauge
A loading gauge defines the maximum height and width for railway vehicles and their loads to ensure safe passage through bridges, tunnels and other structures...
in excess of Plate C or in excess of 16 in 3 in (4.95 m) high were prevented from using the tunnel.
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 gantlet track, and rehabilitating the tunnel drainage system. No fundamental change, however, was made in the tunnel’s difficult geometry. Eventually, the gantlet track was removed due to changes in freight traffic patterns.
Proposed Replacement
In June 2008 the U.S. House of Representatives voted to support a study of the environmental impactsEnvironmental impact assessment
An environmental impact assessment is an assessment of the possible positive or negative impact that a proposed project may have on the environment, together consisting of the natural, social and economic aspects....
of different possible replacement tunnels. On January 28, 2010, $60 million in funding was awarded under the American Recovery and Reinvestment Act to conduct the study, but not the estimated billions of dollars that will be required for a replacement tunnel.
External links
- U.S. Federal Railroad Administration. Report To Congress: Baltimore's Railroad Network, Challenges and Alternatives. November 2005.
- "Part 1: Challenges." Discussing the history and recent state of Baltimore rail infrastructure.
- "Part 2: Alternatives." Discussing possible replacement tunnel alignments along Presstman Street (see page 7-7) or US Route 40, among others (see page 7-9).