The MTA plans to unclog two of the most vexing points where subway trains get delayed due to multiple lines converging or other structural constraints in the system, it announced in a new report out Wednesday.
The report both highlights projects the agency is already undertaking to address two of the major chokepoints, known as bottlenecks, and identifies 25 others that it can work to eliminate in the future. Bottlenecks — arising from issues with interlockings, terminals, track configuration, and legacy signal systems — can cause delays that ripple throughout the system and trigger the familar “we are delayed due to train traffic ahead of us” announcement.
“These bottlenecks create delays, even on good days, when everything is running according to plan,” said Liam O’Connell, a senior planner at the MTA, during the agency’s July board meeting on Wednesday.
“You’ll know these delays when you’re waiting on a train somewhere and you hear an announcement like, ‘we’re waiting on a train to cross in front of us’ or the ‘train across the platform will be leaving first,'” he continued. “These small holdups mean that your travel time on the train is inconsistent from day-to-day and also that the waiting time for riders at all of the stations further down the line is inconsistent with the schedule.”
The report’s findings build upon the MTA’s recent operational changes to the F and M lines, which involved swapping their routes between Manhattan and Queens late last year. The change led to a 4% decrease in running times and fewer conflicting merges at the Queens Plaza station, agency officials reported on Monday.
“Folks at the Roosevelt Island Station are for the first time in a long time having trains that don’t arrive completely packed in the station in the a.m. peak,” said MTA Chair and CEO Janno Lieber during the same meeting.
The two projects already underway aim to clear bottlenecks on the B, D, N, R, and Q trains in the area between the Brooklyn side of the Manhattan Bridge and the DeKalb Av station; and on the 2, 3, 4, and 5 trains east of the Franklin Av station, according to the report. Both are funded by the MTA’s current 2025-2029 Capital Program.
The issue at DeKalb Av arises from an interlocking where the B, D, N, and Q trains cross paths after coming over the Manhattan Bridge. The merging of the B and D trains to join with the Q and N trains, respectively, can cause delays, as one train must wait for another to cross in front of it.
Those delays can quickly cascade.
“These merges at DeKalb … are what create the delays that you might remember if you are descending the Manhattan Bridge,” O’Connell said. “You’re on a D train, say, stopped, waiting for an N train on the other side of the bridge to pass to get to the switch in front of you.”
O’Connell said that tower operators individually route each train through the interlocking due to their use of nearly a century-old signals, which can further compound delays.
The same problem occurs with Manhattan-bound trains as well, according to the report.
The MTA is working to clear the bottleneck by installing its modern Communications-Based Train Control (CBTC) signal system on the B and D lines between DeKalb Av and 47-50 Sts-Rockefeller Ctr. It is planning to award a contract for the work by the end of this year.
The new technology will help clear the issue by allowing trains to run faster and closer together through the interlocking. Its installation will also give the agency the chance to replace aging switches in the interlocking, which will could help trains go through at higher speeds.
The 2, 3, 4, and 5 trains face a similar bottleneck at the Nostrand Junction interlocking just past the Franklin Av station, where the 2 and 5 trains and 3 and 4 trains split into different branches headed for Flatbush Av and New Lots Av, respectively. Because the 5 train currently must cross from the express to local tracks, it ends up on the same track as the 2 and 3 trains for about 150 feet, sparking cascading delays.
“It is that crossing movement of trains at Nostrand Junction that contributes to that bottleneck,” O’Connell said.
The MTA plans to fix this by updating the switches in the interlocking and realigning the trains that run through it. Instead of the current configuration, the plan would clear the way for the 5 and the 3 trains to swap places, with the former running along Eastern Parkway with the 4 train and the latter going down Flatbush with the 2 train.