Limited track options to redirect rail cars during maintenance

Metrorail and other subway or “heavy-rail” track systems have special track configurations that can redirect or temporarily store rail cars during maintenance and emergency situations. Metrorail’s existing two-track system has a limited number of tracks to redirect trains during maintenance efforts, potentially causing a transit knot.

Crossover track Allow trains to single-track during incidents or track work (Drawing is schematic) Station Pocket track Redirect trains to opposite track; store maintenance equipment Spur track Used for rail car storage Pocket and crossover tracks in Metrorail’s system MILEAGE LENGTH OF ALL LINES* POCKET TRACKS** 7 5 11 Unavailable 12 WMATA San Fran. BART Chicago CTA New York MTA Boston MBTA 117.8 108.8 103.4 230.8 37.7 *Total length of all lines, not tracks in passenger service, counting mileage in one direction only to the nearest 0.1 mile. **Does not include pocket tracks located at the end of lines. Crossover track Pocket track Used for rail car storage Station Allow trains to single-track during incidents or track work Redirect trains to opposite track; store maintenance equipment Spur track (Drawing is schematic) Glenmont KEY Shady Grove Pocket track Greenbelt Crossover track Fort Totten Wiehle - Reston East New Carrollton Gallery Place Stadium - Armory Rosslyn Largo Town Center Metro Center Vienna East Falls Church L’Enfant Plaza Pentagon Branch Ave. King St. Franconia - Springfield Huntington YEAR OPENED MILEAGE LENGTH OF ALL LINES* MAXIMUM NUMBER OF TRACKS IN A STATION POCKET TRACKS** WMATA San Francisco BART Chicago CTA New York MTA Boston MBTA 1976 1972 1947 1904 1901 117.8 108.8 103.4 230.8 37.7 2 2 4 4 2 7 5 11 Not available 12 *Total length of all lines, not tracks in passenger service, counting mileage in one direction only to the nearest 0.1 mile. **Does not include pocket tracks located at the end of lines. Note: Boston streetcar service began in 1897 but heavy rail service was not available until 1901. Crossover track Pocket track Used for rail car storage Station Allow trains to single-track during incidents or track work Redirect trains to opposite track; store maintenance equipment Spur track (Drawing is schematic) KEY Glenmont Pocket track Crossover track Shady Grove Greenbelt Fort Totten Wiehle - Reston East New Carrollton Gallery Place Stadium - Armory Rosslyn Largo Town Center Metro Center Vienna East Falls Church L’Enfant Plaza Pentagon Branch Ave. King St. Franconia - Springfield Huntington YEAR OPENED MILEAGE LENGTH OF ALL LINES* MAXIMUM NUMBER OF TRACKS IN A STATION POCKET TRACKS** WMATA San Francisco BART Chicago CTA New York MTA Boston MBTA 1976 1972 1947 1904 1901 117.8 108.8 103.4 230.8 37.7 2 2 4 4 2 7 5 11 Not available 12 *Total length of all lines, not tracks in passenger service, counting mileage in one direction only to the nearest 0.1 mile. **Does not include pocket tracks located at the end of lines. Note: Boston streetcar service began in 1897 but heavy rail service was not available until 1901.

Deep underground stations and tunnels vulnerable to water intrusion onto tracks

Some maintenance issues correlate to tunnel depth. Two kinds of underground tunnel and station construction methods used to build the system were cut-and-cover and rock tunneling. Rock tunneling was less disruptive of dense urban areas during construction than shallow cut-and-cover sections. All of the underground stations are beneath the water table level. The deeper the tunnel, the more vulnerable it is to water intrusion because greater groundwater pressure can cause water to enter faster.

Cut-and-cover construction Of the underground Metrorail stations, 37 were constructed using the cut-and-cover method — a more cost-effective infrastructure option than rock-tunneling but also more disruptive to urban areas. The process involved digging along city streets, building the tunnels and stations and then covering everything back up. plastic sheathing Rock tunnel construction Eleven underground stations were constructed by boring through rock. A waterproofing technology called the New Austrian Tunneling Method has been used to weld sections of a plastic sheathing layer between geotextile material and a concrete lining. Cut-and-cover and rock tunnel stations in Metrorail’s system New Austrian Tunneling Method Rosslyn is rock tunnel and cut-and-cover construction. WMATA began installing waterproofing sheathing in NATM underground rock tunnels in the early 1980s after older tunnels experienced water intrusions and corrosion. The sheathing has since been used to help waterproof soft ground tunnels and stations as well. plastic sheathing Cut-and cover-construction Rock tunnel construction Of the underground Metrorail stations, 37 were constructed using the cut-and-cover method — a more cost-effective infrastructure option than rock-tunneling but also more disruptive to urban areas. The process involved digging along city streets, building the tunnels and stations and then covering everything back up. Eleven underground stations were constructed by boring through rock. A waterproofing technology called the New Austrian Tunneling Method has been used to weld sections of a plastic sheathing layer between geotextile material and a concrete lining. KEY The New Austrian Tunneling Method (NATM) applies Cut-and-cover (37 stations) Glenmont flexible plastic sheathing Wheaton between tunnel surfaces Forest Glen Rock tunnel (11 stations) and concrete liners to prevent water infiltration. New Austrian Tunneling Method Medical Center Georgia Ave.- Petworth Rosslyn station is a combination of rock tunnel and cut-and-cover construction. used for waterproofing Columbia Heights Dupont Circle Gallery Place Union Station Tysons Corner Rosslyn Stadium - Armory Metro Center East Falls Church Ballston Capitol Heights L’Enfant Plaza WMATA began installing waterproofing sheathing in NATM underground rock tunnels in the early 1980s after older tunnels experienced water intrusions and corrosion. The sheathing has since been used to help waterproof soft ground tunnels and stations as well. Pentagon Congress Heights Crystal City King St. plastic sheathing Cut-and-cover construction Rock tunnel construction Of the underground Metrorail stations, 37 were constructed using the cut-and-cover method — a more cost-effective infrastructure option than rock-tunneling but also more disruptive to urban areas. The process involved digging along city streets, building the tunnels and stations and then covering everything back up. Eleven underground stations were constructed by boring through rock. A waterproofing technology called the New Austrian Tunneling Method has been used to weld sections of a plastic sheathing layer between geotextile material and a concrete lining. Glenmont KEY Wheaton Cut-and-cover (37 stations) Forest Glen The New Austrian Tunneling Rock tunnel (11 stations) Method (NATM) applies flexible plastic sheathing between tunnel surfaces New Austrian Tunneling Method and concrete liners to prevent water infiltration. used for waterproofing Medical Center Georgia Ave.- Petworth Columbia Heights Dupont Circle Rosslyn station is a combination of rock tunnel and cut-and-cover construction. Gallery Place Union Station Tysons Corner Rosslyn Stadium - Armory Metro Center East Falls Church Ballston Capitol Heights L’Enfant Plaza WMATA began installing waterproofing sheathing in NATM underground rock tunnels in the early 1980s after older tunnels experienced water intrusions and corrosion. The sheathing has since been used to help waterproof soft ground tunnels and stations as well. Pentagon Congress Heights Crystal City King St.

Cumulative track mileage construction over time increased maintenance demands

Metrorail opened its first segment of the Red Line in 1976 between Rhode Island Avenue and Farragut North. After that, construction of six different lines continued during several decades. The opening of the Silver Line in 2014 extended the system's length to 117.8 miles.