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The chart displays the locations of physical limitations that cause capacity problems or "choke points" between Washington, DC and Boston. As in Charts A-1 and A-2, a chart of twelve boxes linked from left to right, representing the stations along the Northeast Corridor with the number of tracks between each station and a brief description of the types of constraints that place limitations on the capacity of service as follows:

Between Washington, DC and Baltimore there are three tracks and the limitations on capacity are affected by:

• BWI Platforms
  
• MARC trains

Between Baltimore and the major intermediate point there are two tracks and limitations are affected by:

• The two tracks traffic; requires train tracks to pair down from three tracks to two tracks
  
• The two tracks require "OVERTAKES" (designated trains move aside to let other trains pass through)
  
• Bridges

From the intermediate point north to Philadelphia, there are four tracks. From the intermediate point south, trains pair down from four tracks to two tracks.

Between Philadelphia and the major intermediate point between New York Penn Station there are four tracks and the limitations on capacity are affected by a capacity limitation at Metropark.

From the intermediate point north to New York Penn Station there are two tracks and the limitations on capacity are affected by:

• Construction at Secaucus.
  
• North River tunnel capacity. (It narrows to two tracks and has to accommodate all the commuters from the intercity traffic.)

Between New York Penn Station and Harold interlocking there are four tracks and capacity is affected by:

• East River Tunnels
  
• Penn Station capacity
  
• Long Island Railroad volume
  
• New Jersey Transit volume
  
• Amtrak volume

Harold interlocking is a major switching point. Capacity is effected by:

• Four tracks on the east end
  
• Two tracks on the north end

Between Harold interlocking and New Rochelle there are two tracks and capacity is affected by:

• Hell Gate (a critical bridge crossing)
  
• New construction taking place affecting metro trains to and from the north and Amtrak

Between New Rochelle and New Haven there are four tracks and capacity is affected by the following issues relating to METRO NORTH operations:

• Slots consumed by commuter traffic
  
• Engineering work
  
• Ownership - Metro North owns the tracks and controls the traffic flow (i.e. including Amtrak trains)

Between New Haven and Providence there are two tracks and capacity is affected by:

• Limitation on engine changes (Some operations may require a change from electric engines to diesel engines.)
  
• Shore Line East - there is track congestion
  
• Moveable bridges that sometimes have to open for boat traffic
  
• Providence and Worcester trains
  
• TF Green Airport at Providence
  
• Rhode Island Department of Transportation
  
• 34 train limit

Between Providence and an intermediate point between Providence and Boston there are two tracks. The high number of Massachusetts Bay Transit Authority (MBTA) commuter rail train operations at times exceeds the capacity of the two tracks.

Between the intermediate point and Boston there are three tracks and capacity is affected by:

• MBTA trains
• South Station capacity
  

Return to Appendix A-3