Tag Archives: core capacity

More train doors and wider doors will help WMATA capacity

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):

WMATA Capacity Analysis, comparison of ingress/egress for rail cars in peer systems.

WMATA Capacity Analysis, comparison of ingress/egress for rail cars in peer systems.

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.

Adding to Metro’s Core Capacity

Greater Greater Washington’s always had some great fantasy transit discussions – whether talking about the New Blue line, more fantastic visions, or even the multimodal vision for Baltimore and DC.  Over the last few days, the fantasy discussions have started again.  Though these are not always the most realistic discussions, they’re a great starting point for larger discussions about the role of transit in the transportation system in the city, and more importantly they discuss what kind of city we want to have.

This past week’s discussions have focused on the idea of a new Yellow line – originally posted here, along with my response.   The entire premise of separating the Yellow line from the Green line (at least as I understood it) was to increase the maximum capacity of both lines – the same premise behind the idea of separating the Orange and Blue lines.  That way, both colored lines would have full capacity for their entire length.  Doing such a project would also have ancillary benefits, such as adding redundancy to the system with multiple tracks on fairly similar routes, as well as opening up new areas to Metro service (such as adding Metro service to H Street NE with the New Blue line).  Each of these ideas is worthwhile, though slow to implement.  Given the facts that Metro is already straining to handle the crowds along the Orange line though the RBC, focusing on this kind of long term planning is important.  Building new subway lines will take a long time, and with Metro expected to reach capacity sometime between 2025 and 2030, starting the planning process now is vitally important (i.e. Metro was recommended as the preferred alternative for the Dulles Corridor in a 1997 report – the full line is now set to open in 2016 – nearly 20 years after the fact).

With that in mind, proposals that involve a great deal of capital construction must have a long term plan behind them to justify the investment.  The idea of separating the Blue and Orange lines is a good start.  Having a longer term plan to separate the Green and Yellow lines is also a good idea – even better would be to combine those efforts sowe have a nice 50 year map to follow for Metro’s development over time.

The lack of this kind of focus and long term vision troubles me with GGW’s latest series of posts about adding new trackwork in downtown DC.  The premise is a simple question: is there a simpler and cheaper way to add core capacity to Metro without building the entire New Blue line?

How about separating the Yellow Line instead? The Yellow Line plan Dave Murphy suggested last week, and some of your comments, suggest a possibility. If we separate the Yellow and Green lines in DC, then Metro could put many more trains over the 14th Street bridge. According to Metro planners, this option would involve building a shorter subway tunnel from the 14th Street bridge to the Convention Center along 9th Street.

While the tunnel at Rosslyn is already at its capacity, the 14th Street bridge isn’t, because all its trains must merge with Green Line trains from Branch Avenue. Metro can squeeze a few more Yellow Trains in if they reduce Blue trains, but not that many. If the trains didn’t have to compete with the Green Line, the 14th Street bridge could carry many more trains from Virginia.

The second iteration of the idea also generated a great deal of discussion:

If we could run more trains over the 14th Street bridge, where would they go in Virginia? I can see two possibilities: convert the Arlington Cemetery segment to a shuttle train, or add connections to route the Silver Line over that segment as well as the Blue Line.

Both of these ideas are intruiging from an academic perspective, but completely lose sight of why you’re adding core capacity in the first place.

Remembering that the whole point of the New Blue line is to separate it from the Orange line tracks it shares through DC, the reason it gets brought up first is due to the popularity of the Orange line in Northern Virginia.  This GGW idea is an attempt to solve that same problem by essentially starting on a new Yellow line.  You’re essentially building half a subway, except that you’re building the New Yellow line first when the Blue line is the obvious choice.

If you’re going to put shovels into the ground, you might as well make sure that the plans have long term significance.  Metro’s genius is that it was concieved as an entire 100 mile system.  Even so, it functioned well before the full system was complete.

WMATA should take the same step here.  If you want to add new capacity to downtown DC by building half of a new subway, just start building the new Blue line – and do it in phases.  The first phase (say, from Rosslyn to the Connecticut Ave station) would accomplish the same thing – freeing up core capacity on the Orange (and Silver) line, as well as delivering Blue line riders to the core of downtown.   However, unlike the 9th street proposal, the Blue line would be readily expandable at a later date, much like how the Mid City portion of the Green line was completed in phases (with U Street opening in 1991, while Columbia Heights didn’t open until 1999).   Ideally, you’d like to do it in one fell swoop, but the entire premise of this idea is that the funds to do such a project aren’t there.  So let’s at least plan it with expansion in mind.

With that said, the idea of a new Yellow line isn’t a bad one at all, even if the timing isn’t quite right.  However, using 9th street doesn’t make a lot of sense when you already have lines along 7th and 12 streets downtown, and along 14th street in Columbia Heights.  The alignment proposed in the original post makes a lot more sense when viewed with a long-term lens.  A 9th street alignment would indeed be redundant, but almost too redundant – it wouldn’t open up any more area to Metro service, such as the transit poor Washington Hospital Center.  A North Capitol/Georgia Ave route would provide redundancy for both the eastern Red line, the whole of the Green line, and open up a major commercial street to Metro.  This line could also be phased in over time, initially operating as just a partial segment.

As Burnham said, “make no little plans.”  If you’re looking for incremental physical improvements, I’d opt to ensure that they’re part of a larger plan.  The final result will be far better for it.