It’s always fun to stumble across official analysis that mirrors your own – even if some of the conclusions differ.

With a hat tip to Kurt Raschke, I came across this document outlining WMATA’s challenges in providing capacity in the core of the system. Most of the white paper focuses on potential increases in rail capacity from changing WMATA’s signalling system from the current fixed-block system to a CBTC-based moving block system (they do not find a large practical boost in capacity from such a change).

The document is part of making the long-term case for additional rail tunnels through downtown. In order to justify that expense, they are addressing some of the preliminary alternatives to squeeze more capacity out of the existing system (organization before electronics before concrete). From the executive summary:

As train and station congestion worsens, a question logically posed by stakeholders and the public is” “Why can’t Metrorail add more trains to relieve the crowding?” The fundamental purpose of this White Paper is to present the root causes of Metrorail capacity constraints that limit service expansion in the core.

One thing that jumped out at me was the suggestion of procuring new rail cars with more doors and wider doors – a suggestion I’ve made before.  More doors can better handle boarding and alighting, reducing station dwell times, and thereby improving both capacity and reliability. The benefits are substantial (emphasis added):

[T]he benefits in terms of reduced dwell times for a 60 second dwell time would likely be in the range of 8-12 seconds (a 20-30% reduction in that portion of the dwell associated with passenger alighting/boarding with no effect on the base door cycle time dwell component of about 20 seconds). Assuming all cars of all trains have four doors per side, this is equivalent to a throughput gain of about 2 trains per hour.

The white paper also includes this table (which bears a striking resemblance to one I put together several years ago):

Despite the obvious benefits of this change, the white paper downplays the potential for increasing the system’s overall capacity. Addressing them one by one:

As shown in Table 9, relative to car length, the boarding and alighting capacity of Metrorail vehicles closely matches the capabilities of peer systems’’ vehicles. WMATA’s rolling stock matches the median of those sampled for both the number of doors per unit car length, and the total door width per unit car length, though both of these values are slightly below the mean. While procuring or modifying vehicles to increase the number and size of doors may conceivably increase the rate at which passengers could board and alight, it would be an unconventional method for increasing total passenger carrying capacity.

I wouldn’t agree with the statement that all of these railcars closely match. In the rightmost column (inches of door width per foot of car length), you’ll see that the busiest of WMATA’s peers have a door capacity 50% greater than WMATA, or more.  The difference between WMATA’s 2 in/foot and Toronto’s 3.2 in/foot is huge.

Second, the major benefit to adding more doors isn’t an increase in absolute capacity, but to improve reliability and the passenger experience. More doors means a smoother flow of passengers on and off trains. Faster station dwells, particularly at crowded transfer points, reduces the likelihood of passengers holding doors or missing a train because of a lack of time to board.

Next: the time required to make this change.

Although this rolling stock change could be implemented incrementally as each Metrorail fleet type is retired, full implementation would require over 40 years due to the life cycles of the multiple Metrorail fleets.

All the more reason to get started with a four-door design for the next rail car series! And another reason to consider the design of the 7000 series a missed opportunity.

What about lost seating?

Second, implementing a new railcar design with four doors per side would result in a net seat reduction of approximately 28 percent, requiring more customers to stand.

I’m not sure where this calculation comes from; a cab car (A-car) from WMATA’s 7000 series seats 64 with the current arrangement and 58 with a longitudinal-only seating array. Toronto’s Rocket cab cars feature a similar rail car size (75 feet long) and feature four wide doors per side; they still manage to provide 53 seats, representing a 17% decrease over the 7000 series seated capacity.

WMATA’s own actions show that seated capacity isn’t a primary consideration. WMATA has been slowly reducing the number of seats per rail car series and increasing standing room with each new version; the original 1000 series had seating for 82; the 2000 series sat 76 per car; the 5000 series seats 68, and the 6000 series seats 64.

Given the stated goal of this white paper to determine potential for long-term solutions to WMATA’s core capacity challenges, I hope they don’t discard the idea of adding more doors to the future railcar fleet. Combined with some other suggestions, there’s a great opportunity to improve both the system’s capacity and reliability.