That is the question that New York City's MTA is facing in determining how to make services more efficient.
Commuters have one common objective, that is to go from point A to point B. That is particularly tricky on a metro system - the infrastructure simply cannot be designed to accommodate all point-to-desired-point journeys. With big interchange hubs (such as connections with intercity and Eurostar services at King's Cross St. Pancras in London or services to the Mainland Chinese border from Admiralty in Hong Kong - both of which are the busiest stations on their respective subway networks), it is not unusual to have to interchange between different metro trains worldwide. Of course, interchanging does add time to the commute (although, this has been minimised on metros that utilise cross-platform interchanges at key interchange stations). Yet, the idea of having to change trains is generally accepted when taking the metro.
Then comes the idea of interlining. It is a heavily used feature of the New York City Subway. Interlining offers a wider variety of direct, one-seat rides because different trains can directly cross points to traverse different routes all from the same set of platforms. For example, if you are at 59th Street-Columbus Circle, interlining just south of the station allows you to head down 8th or 6th Avenues as well from the same set of platforms - allowing easy access to popular tourist destinations such as the Rockefeller Center or the major transit hubs of Port Authority Bus Terminal and Penn Station. Or if there is a broken train between Columbus Circle and 50th Street, merging points just north of Columbus Circle allow trains to traverse tracks and continue a service - far better than a continuous backlog of trains, delays and even line suspensions that other metros are susceptible to.
It is worth noting that route-sharing is not unique to New York - in London, the Hammersmith and City, Circle and Metropolitan lines share tracks eastwards from Baker Street to Liverpool Street, with the Circle line sharing tracks in its route entirety. However, it is extensive in New York City - around 85% of routes on the NYC subway share tracks with other routes.
Interlining has been somewhat controversial with the interlocking delays attributing to poor punctuality rates (in 2023, the Subway had an on-time performance of 84.5% - the Tube had a 91.1% arrival rate within 3 minutes) because of the bottlenecks at these junctions. In fact, various visions online have prompted calls for the MTA to 'de-interline' on the basis that individual line capacity would increase as a result of higher service frequency as opposed to complex track switching to serve different routes. Pedestrian Observations have also claimed that supposed 'higher frequency' would entice more commuters to travel by train.
I have mixed feelings regarding the visions of de-interlining. Ridership of the subway in 2022 averaged daily of 3.2 million. This is far below pre-pandemic highs of around 5.5 million in 2019 but shows a very different aspect compared to other similar-sized cities - that the percentage of public transport trips made by metro is far higher by bus.
City/Region of comparison to New York City | Percentage of public transport trips made by Metro | Percentage of public transport trips made by bus |
New York City (circa. 8.5 million) | 71.15% | 22.79% |
London (circa. 9 million) | 26.52% | 41.89% |
Hong Kong (circa. 7.4 million) | 47.14% | 49.38% |
The table above shows the share of public transport trips in 2019 made in New York City, London and Hong Kong*. The unique composition of New York City's subway and rail services means that more than double of public transport users in the city are using subway over bus. Even with factoring in London's suburban rail services (~28.62%), New York's subway share usage dwarfs London and Hong Kong. I struggle to see how de-interlining NYC's subway service would entice more users, seeing as usage pre-pandemic was extremely high - it is evident that there are other significant factors (COVID-19 especially as evident in Europe and North America) have played a role in usage decline - New York City has yet to match pre-pandemic usage levels.
The fact that de-interlining would not work as a result of 'loss aversion' - that is, a preference to not lose something rather than gain potential benefits - is true to an extent. Yet, it is more than loss aversion. Removing a wide variety of routes (or 'trains') and replacing them with individual lines would not encourage more commuters to switch to trains because one-seat rides would be extremely limited and could actually dissuade users - therefore, I believe the opposite (to what the supposed benefits are of de-interlining) would happen.
To interline or 'not to interline'? There are advantages and disadvantages to both options but de-interlining would, in my opinion, be unfeasible for New York City's infrastructure and for a system that serves an extremely dense and busy area as Manhattan. In addition, interlining offers a different method of subway travelling - one that, although the Big Apple has taken to the extreme, makes journeys more accessible without the need for interchanging. Of course, there are options to create intentional, interchange hubs outside of Midtown/Downtown Manhattan (DeKalb Avenue or even an interchange between Queensboro Plaza and Queens Plaza) but whether these would be effective and would be of more benefit than loss compared to current alignment is hypothetical. De-interlining the New York City subway has been touted for a while but its effectiveness is far more complex than what the eye sees.
*statistics retrieved from https://citytransit.uitp.org/, based on 2019 data.
Metro in this case refers to rapid rail transit