Eight-Car Trains on Metro is Equivalent to Widening I-66 in Arlington by Two Lanes

Adding two extra cars to a six-car Metrorail train might not seem like much, but it is equivalent to widening I-66 through Arlington by two lanes. Plus, it’d likely be cheaper and faster for commuters, too.

Sometimes it’s hard to wrap one’s head around how just many people Metrorail can move. But where Metrorail operates in heavily congested corridors, seemingly small improvements can yield big results. In fact, matching the capacity of all eight-car trains system-wide would require 16-18 lanes of freeway into downtown, each way.

Orange Line Metro train from I-66. (Photo by wfyurasko, click for original)

To match the capacity of eight-car trains on Metro, we’d have to widen I-66 in Arlington by at least two lanes. (Photo by wfyurasko, click for original)

In Arlington for instance, going to eight-car trains on the Orange Line as part of Metro 2025 is like widening I-66 by two lanes.  Let’s do the math:

  1. One lane of highway can move around 2,200 cars per hour, at its theoretical maximum.
  2. Today, every morning Metrorail runs about 18 trains per hour eastbound on the Orange Line through Arlington, and about a third are scheduled eight-car trains. That’s a train every three minutes, and equates to around 121 rail cars per hour, or 12,060 passengers per hour.
  3. By 2025 with eight-car trains, Metrorail will be able to run 21, eight-car trains per hour eastbound on the combined Orange and Silver Lines, which equates to 168 cars per hour.
  4. This means Metro 2025 will bring the line’s capacity to 16,800 riders per hour, or an increase of 4,740 passengers per hour.
  5. To accommodate 4,740 more people on I-66 at 2,200 cars per hour, 2 people per car, we’d need 4,740 / 2 / 2,200 = 1.1 highway lanes in each direction.

That means we’d need at least two new lanes on I-66 to match the capacity of Metro 2025. In addition, eight-car trains would be cheaper, and would likely move people faster through the corridor.

  • Eight-car trains on Metro would be over two times cheaper: the estimated cost to widen I-66 works out to about $3.50 per rush-hour trip over the life of the project, whereas Metro 2025 would be about $1.50.
  • Metrorail would likely move travelers faster than I-66 in the end.  Orange Line trains today normally run at around 35 miles per hour, while congested travel speeds on I-66 average around 18 miles per hour. While new highway lanes might move cars faster at first, the improvements would eventually be eroded by growing congestion.

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  1. Bender
    July 18th, 2014 at 11:24 | #1

    That’s great – 2200 few cars on the road if those people took Metro. Since most of those people are coming from Fairfax and beyond, and not within walking distance of a Metro station, WHERE ARE THESE 2200 CARS GOING TO PARK??

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  2. Wiz
    July 18th, 2014 at 11:35 | #2

    What exactly does two times cheaper mean? Two times cheaper than what? Is it the same as half as expensive?

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  3. Matt Lenco
    July 18th, 2014 at 13:23 | #3

    I live near ballston and work in Herndon. It’s a 30 minute walk to Ballston metro from my house 45 minute train to Reston and a 15 minute bus to my office. The total public transporation time, 1 hour 30 minutes. If I drive before rush hour it would be 35 minutes door to door. Public transportation statistics are weak in proving the benefits of piece meal public transporation. If you are going to provide public transportation then you really must address the concern of such a large area.

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  4. July 18th, 2014 at 22:26 | #4

    How would 8 car trains affect Vienna Metro at the end of the line in regards to additional lanes need on I-66 west of the station?

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  5. letmeanswer
    July 21st, 2014 at 10:01 | #5

    ” Since most of those people are coming from Fairfax and beyond, “

    given crush loads in north arlington, more capacity could mean more riders in North Arlington, who would walk to the station rather than driving.

    Also people can take buses to Vienna metro, as many now do. More will when there is BRT service on outer I66.

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  6. Mark
    July 22nd, 2014 at 14:22 | #6

    It’s not rocket science, folks. If you live and work near a metro station chances are good that you will use the system rather than drive. That’s not to say that if you live in Rockville and work in downtown Silver Spring that metro woul be faster than driving given the long Red Line commute.

    Therefore, it boils down to several factors. First, the system itself. Metro was built as a hub and spoke system back in the day when the job concentration was in the District. People in during the morning, people out after work. Well, this has changed over the decades. Moving forward, Metro needs to consider how it’s system is going to effectively and efficiently deal with reverse commutes and burb-to-burb commutes.

    Second, the convenience factor. If it takes me 90 minutes to commute by public transit and only 45 minutes by car then I’m most likely going to opt for the less heinous commute and drive. Likewise, if I have to deal with the hassles and cost of parking, taking transit, even if it takes a bit longer, may be less of a headache.

    Finally, transit-oriented development and sprawl. If VA and MD are hell bent on pushing cul de sacs, strip malls and low density development down our throats, then don’t even bother factoring transit in the picture. These types of development only encourage the use of cars. However, if communities would support higher density development adjacent to or within walking distance to a Metro station then there is hope for transit. There’s no reason why the Rosslyn-Ballston corridor success story can not be replicated in other areas of the region.

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  7. steve strauss
    July 31st, 2014 at 10:10 | #7

    To Bender:

    Some of those 2,200 people can park at Orange line stations. The opening of the Silver line has resulted in some Orange line riders shifting to the Silver line and opening up parking spaces along the Orange line.

    To Justin: Have you included the ancillary costs of the additional rail cars in your cost comparison. The additional rail cars require power upgrades, more storage tracks and additional maintenance bays among other things.

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  8. Justin
    July 31st, 2014 at 10:13 | #8

    @steve strauss Yes, the cost comparison is based on the entire cost of Metro 2025, so it includes all costs associated with 8-car trains.

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