At capacity with room to expand

A number of reports by the MTA, Straphangers Campaign, and other organizations claim that almost every line of the subway is at maximum capacity. While this is true, the subway system has much in the way of hidden capacity, even at rush hours. Although dependent on the amount of rolling stock, population growth, and other factors, it is possible to improve passenger flow, although there are some hurdles to do so.

Of course, there are some lines that are and will be perennially congested, mainly the IRT due to small car sizes but higher demand (Grand Central is, after all, an all-IRT station). Even with the Second Avenue Subway, the Lexington Avenue Line will still be incredibly packed, as will the E with its useful Penn to Midtown routing. Part of the problem is that the system is so old and hasn’t been upgraded to current standards, apart from the L, and even that line has barely made it.

To improve throughout, the MTA will have to aggressively modernize its signalling and automation systems through the implementation of automatic train operation and control (ATO and ATC) as well as communications-based train control (CBTC), currently operational on the L. This will not be easy; the subway is unique in that it runs on both some of the oldest operating technology in use throughout the world and it uses interconnection between lines on a scale seen in few rapid transit networks. The sheer size of the subway system alone makes retrofitting it daunting, both in terms of engineering and finance. Equipping it with CBTC will cost hundreds of millions of dollars, and that’s not counting the inevitable delays that will occur.

However, the advantages capacity-wise of such advanced technology merit the investment. Let’s take the L (as usual) because of its self-contained nature and simple operating scheme, with no branches or express service. Currently, its rush hour capacity is 29,160 people per hour, although crush loading does mean that this number is exceeded. However, with CBTC capability, an additional 11 trains each hour, with a new headway of 2.3 minutes, will increase capacity to 50,544 people per hour, a 73% increase.

The numbers are even more staggering for trunk lines. Let’s take a look at the Lexington Avenue Line under CBTC operation, assuming that it will improve 6 service to 22 trains per hour as combined 4/5 service to 20 per hour. Currently,  the 6 operates every 4 minutes during rush hour (15tph), with an ultimate capacity of 54,960 people per hour. Under 22tph operation, this would increase by 46% to 80,608. In addition, one more train per hour would be placed in express service, resulting in about 5% more capacity. In total, CBTC would allow for 153,816 people per hour on any given stretch of the Lexington Avenue Line, better distributing its 1.3m ridership every weekday.

There is a downside to this: operational cost. The Transit Worker’s Union (TWU), when threatened by one-person train operation operation on the L, was able to block it. However, increasing the total trains per hour will require more train operators, in turn escalating the MTA’s labor costs, something they can’t afford to do. The solution is to implement OPTO during off-peak hours, transferring the conductors that would be working at those times to peak hour work. Also, more rolling stock would need to be ordered so as to ensure that there are enough trains not only to run with lower headways but also in case of breakdowns that extra cars are available.

Overall, CBTC implementation has much to offer the subway system in terms of capacity and improved technology. The investment is necessary to help bring the subway to the 21st century and improve the commutes of millions of New Yorkers.

2 Responses to “At capacity with room to expand”
  1. Alon Levy says:

    You’re getting the capacity numbers wrong. The MTA-defined capacity of an IRT car is 110 people, i.e. 1,100 people per train. Japanese trains define capacity similarly and exceed it by a factor of about 2, so this is more about comfortable capacity than absolute crush capacity. In addition, the current capacity of the subway tracks with present signaling and practices is 30 tph, reduced to 24 tph at Grand Central because of crowding. This is 33,000 people per hour on each track. CBTC means fewer delays due to crowding, so it could get trains closer to 30, or even marginally above 30. (20 tph is very easy, by the way – the L can’t do it without CBTC only because its terminal throat is configured badly.)

    You can’t under any circumstances expect 80,000 passengers per hour without greatly exceeding any reasonable capacity. Again, it’s possible and routine in Tokyo, but why do it?

  2. Phil says:

    It always seemed off that the Tube could get away with incredibly high throughput under SelTrac but the Canarsie Line was limited to 23. I guess the City Hall loop helps with the Lex intervals. Should have checked that better.

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