The importance of more & wider doors for future Metro railcars

CC photo from Stephen Evans

CC photo from Stephen Evans

This week, WMATA awoke to a nice present sitting under the tree. The first of the 7000 series railcars is here. These new cars will expand the fleet, increase the system’s capacity, and replace the oldest railcars in the system. All worthy ends, and all goals that the 7000 series will help meet.

However, like the economists pondering the economic inefficiency of Christmas, I can’t help but wonder what the 7000 series could look like if the gifts under the tree were exactly what you wanted. In that regard, the 7000 series design falls short. The good news is that there will be more railcar procurements in the near future.

The key shortcomings of the 7000 series are not technical (yet! we will need to see how they perform once in service), they are based on policy and assumptions about what a WMATA railcar is. Engineering-driven technical changes include a slight repositioning of the door locations and improved car body crash energy management.

At the same time, the assumption of the car design is to avoid changing the fundamental WMATA rail car concept (three doors per car, lots of seating for a commuter/metro hybrid). This means that the aesthetic changes to the 7000 series aren’t just about the end of Metro Brown. The altered door spacing and adherence to the original concept (three doors per car, three windows between each door) makes for awkward proportions – all in the name of leaving the original concept unexamined.

The good thing about assumptions is that they’re easy to change — once you change your mind. In California, BART struggles with the same legacy of operating a rapid transit/commuter rail hybrid. Despite the shortcomings of BART as a planning/construction agency, BART the operating agency is moving in the right direction. BART’s new rolling stock makes a couple of big changes, such as adding an additional door per car, embracing the rapid transit reality for the system.

Embracing the status quo is easy for any institution. That inertia is hard to overcome. Contrast BART’s changes to the most recent railcar procurement in Chicago, where the biggest changes are in the technical systems and seating layout.

I outlined some key ideas for the 8000 series in a previous post, but I wanted to put some numbers together to make the case for one of the most visible changes: wider doors, and more of them. The chart below summarizes the key dimensions from a selection of railcars:

Railcar Door Comparison

A Google docs spreadsheet with the above data is available here.

I chose the cars on this list for a variety of reasons. I mentioned RATP’s MP-05, used on the now fully automated Line 1 in Paris, and Toronto’s Rocket in a previous post. BART’s inclusion shows both old and new cars, demonstrating what can be gained from change. Using BART as a comparison point for WMATA is also useful due to the similar age and history of the two systems. And, as a counterpoint of traditional mass transit, I included examples of relatively new cars from New York’s A and B division.

Each of these examples represents a somewhat pragmatic choice; I wanted to include others but could not easily find online specifications on door opening widths. Basic dimensions on car/train length is easy to find, but door opening width is harder. Transport for London is one exception, with excellent online information from the agency itself, rather than from third parties. London’s new S7/S8 cars would be a good example to include, but TfL has not yet updated their rolling stock information sheet to include them.

Online sources:

The table shows  the impact of both the total number of doors, as well as the width of the doors. WMATA’s 50 inch doors are relatively narrow; all of the other examples are at least a few inches wider. The one exception is New York’s R160, but the R160 makes up for those narrow doors with overall numbers: Four door openings per 60′ rail car, compared to WMATA’s three doors per 75′ car. Each door on the MP-05 in Paris is 1.65 meters wide, showing how wide you can go – wider than WMATA by more than a foot.

The big reason to add doors is to improve/reduce station dwell time. The rightmost column illustrates the benefits of many wide doors: more space available to move between the train and the platform. When an 8-car WMATA train arrives at a platform, passengers must squeeze into 16.67% of the train to board/alight. Contrast that to the MP-05s used on Line 1 in Paris, where 32.9% of the train is available for passengers to pass through from train to platform. To put it another way, if WMATA wanted to offer that same permeability between the train and platform without changing door width, they would have to double the number of doors.

Line 1 in Paris is an exceptional case, where RATP is attempting to squeeze every last bit of capacity out of century-old tunnels. In the traditional rapid transit cases, each of the New York examples is greater than 25% door width to platform length. Toronto’s Rocket shows what WMATA would need to do to get to that standard: four doors per car, and modestly widen the doors to ~60′ per opening.

BART’s new rail cars won’t achieve the 25%+ of Paris, New York, or Toronto; but adding the third door to their new rail cars will beat WMATA at 19.3% and offer a substantial increase from the two-door model.

A simple re-evaluation of what WMATA’s assumptions about what a  rail car is can go a long way towards the goal of maximizing the capacity of the existing system.

2 comments to The importance of more & wider doors for future Metro railcars

  • The WMATA board brought up the issue of more doors per car during the 5k car procurement process. The engineering staff shot the idea down because of the added weight needed to maintain the structural integrity of the car body.

    All of WMATA’s rolling stock is of a monocoque type design. The body of the car is an intrical part of the structure of the car.

    In order add more and or wider doors one have to abandoned monocoque type design and go with a box on frame design. Such a design would likely weight in at or above the maximum weight specification of the elevated infrastructure.

    I will also note that ever successive car procurement made by WMATA has been heaver then the previous. The 1ks when new weight in at 71,960 lb, the 7ks weight in at 80,000 lb.

  • Alex Block

    Sounds like a great challenge for the engineers to take on.

    The weight issue seems like something that can be solved. The Toronto Rocket cars are similar dimensions to WMATA (~75′ long) yet still only weigh in at ~75,000 pounds per car, while still featuring more doors and wider doors than any of the WMATA cars.

    I’ll bet it’s true that modifying the basic design for the 5000 series wasn’t a great way to accomplish this task, but for the future 8000 series car, there is the opportunity for a clean-sheet redesign in order to address all of the issues and ensure that the rail cars themselves aren’t a constraint to maximizing the capacity of the existing system.

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