Validating Green Line Travel Time Estimates

green-line-sim-full-accel

Following my post last week, Bill Lindeke posted a comment which he summed up as, “What is the theoretical shortest possible run time for the Green Line?

That’s a really good question, since it sets a guidepost for what can realistically be achieved from changing signal timing along the route, and helps us to understand the assumptions that planners of the line originally made.

Of course, the answer depends on exactly how theoretical you want to get. I decided to do a simple simulation based on what speed limit signs I could see along the route. I had started taking attention of them a few months ago as they went up, but spent a few evenings this past week trying to verify the information I already had and to add more to it. Unlike roadways where you typically have a single speed limit over great distances, rail lines tend to have special speed limits for each curve, junction, and other special areas. I also made an assumption that station stops would average 20 seconds.

The main leg of the Green Line along University Avenue is mostly set at 35 mph, though there is a curve at Fairview avenue set for 25. Other curves on the line are mostly set at 10 or 15 mph. Cars and trucks tend to naturally slow at sharp turns, but they move through pretty quickly. The slower speeds that trains take through bends tend to be more pronounced, since the trains themselves are often a lot longer than the curve itself.

As seen in my graph above, it looks like a train could make the run from Target Field to Union Depot in under 38 minutes if it wasn’t encumbered by signals. That includes downtown Minneapolis—my simulation had the train crossing from Target Field to Downtown East station in under 5 minutes, or about 3 minutes faster than the Blue Line is scheduled to take today. That instance also assumed that the LRV operators were extremely good at starting and stopping their trains, starting to decelerate at the precise moment needed to hit the platform dead-on. In the interest of safety, a 38-minute end-to-end time while making all stops should probably remain theoretical.

I did take one step beyond, looking at what might happen if there was an “express” version of the Green Line, which only ran end-to-end, making zero intermediate stops. Here’s the result:

green-line-sim-express

28 minutes from end to end, if you had an operator with nerves of steel and didn’t get held up by signals or other traffic. I’ve heard people ask about express trains on the Green Line in the past, and have tended to brush it off as an unwise idea. According to these two charts, it might be possible to save 10 minutes on the trip, but the complexity of switching from track to track to pass other trains would make it very vulnerable to delay, and would probably have a negative impact on regular trains. They’d also have to run pretty often in order to get benefit from that 10-minute time savings. Running express traffic only every half hour, for instance, would probably be a net loser all around.

Here’s another graph where I attempted to be a bit more realistic, assuming that train operators would only accelerate and decelerate their trains at 50% of the maximum (full service acceleration/deceleration is 3.0 mph per second, though emergency braking is greater). The result was a run time of 41 minutes, which sounds pretty familiar:

green-line-sim-50pct-accel

Based on that and my first graph, it seems that planners of the Green Line expected some very strong signal coordination, priority, or preemption (whatever word you want to put on it), allowing trains to travel with a minimal amount of delay. I believe it’s fairly customary to set schedules around a simulated time based on best-case travel time, plus a fudge factor of 10% or so. Of course, in this case, any fudge factor mostly gets eaten up just by delay in downtown Minneapolis (where there hasn’t been any signal coordination for the Blue Line, as far as I can tell).

There are several things that may be different as built in the real world compared to how they were originally set up in computer models for making estimates. It seems pretty likely that that the three stations added to the line late in the process (Hamline, Victoria, and Western in Saint Paul) weren’t included in the planners’ simulations. That probably contributes to about one and a half minutes of extra time with the way I set things up. I also seem to remember that the Washington Avenue Bridge was originally going to allow trains to go relatively fast (perhaps 45 mph), but as far as I can tell, it’s limited to 25 mph for trains. There may be other changes along the route that were never put into the schedule simulations.

Finally, since this all involved calculating stopping distance, I’ll make a note about safety around light-rail vehicles—assuming a 2-second reaction time and normal braking, it takes 400 feet for a 35-mph train to stop, or 2/3rds of a long block along University Avenue. Even with emergency braking, it could take 280 feet or more for a train to come to a halt, so keep your eyes open when visiting the Green Line.


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13 Responses to Validating Green Line Travel Time Estimates

  1. Steven Prince June 6, 2014 at 9:20 am #

    I understand this to mean the train ride is going to take 45 minutes – considerably longer than getting in a car and driving. There are many constraints on choosing to drive (parking for one), but this a sharp contrast with the opening of the Hiawatha Line, which allowed a downtown to airport run faster than driving.

    The debate decades ago about where the Green Line should go – many thought University Avenue was not the optimal choice – raised this travel-time issue, as well as the impact on local businesses.

    I was on University this week and was struck by how-much on-street parking was gone and how many local businesses lacked off-street parking. Many of those buildings are now obsolete and will have to be replaced with buildings incorporating off-street parking – not a very urban outcome. Go take a look at Big Daddy Barbecue (in my estimation the best in the Cities) at University and Dale and ponder whether this business is going to be able to survive in its present location.

    The history of LRT planning in our region is scandalous, and the results consistently sub-optimal. It is too bad that the reporting on these issues in our local media rarely meets the quality of posts like this one.

    • Adam Miller
      Adam Miller June 6, 2014 at 9:39 am #

      What? Hiawatha from downtown to airport is not faster than driving. At least not unless you’re stuck in rush hour traffic.

      But again, how fast you can get from end to end is largely beside the point for this line. Very few people are going to be making that trip as a commute and even if they are, not having to pay for parking when you get there is probably a bigger consideration than the trip time.

      And, of course, as Tony covered (http://streets.mn/2014/06/03/the-green-line-is-not-a-commuter-rail/) lots of Green Line trips are going to be less than the full length of the line. The hole point of this route is to allow people to get to things along the way, not just from end point to end point. Which is how transit should work to maximize its value.

      Finally, I really don’t understand the thinking that says businesses will be harmed by having a new, higher capacity transit service on their doorstep. Its going to bring them customers, not cost them customers.

      • Mike Hicks June 6, 2014 at 10:21 am #

        You guys mentioned speeds along Hiawatha, which reminded me of something that’s been lurking in the back of my mind — How much do people who use the Blue Line really care about its travel time today? It had also been expected to be faster when it started, but remains popular. I’m not sure where to come down on whether driving or taking LRT is faster for getting to the airport — if you’re along the line, they’re both pretty comparable. LRT’s raw travel time is typically longer than driving, particularly since the airport stations are each pretty far from their respective terminals. However, cars need to be parked when arriving at the airport, and many people choose to park at Terminal 2 when flying from Terminal 1, or even go off-site for parking, so LRT often wins in terms of total time and cost.

        We’ll see how people settle in with the Green Line. If we revisit the question of travel time in a year or two, will people still be grumbling? There are lots of destinations along the route, and so it has a greater value in tying the whole corridor together rather than just the endpoints.

        • Andrew B June 6, 2014 at 3:30 pm #

          I’ve been taking the Blue Line for years and skipping having to park downtown, at the airport, or at MOA is always worth more to me than a few extra minutes on the train to reach the destination.

          • Adam Miller
            Adam Miller June 6, 2014 at 3:45 pm #

            Parking is free at MOA, and I’ve walked a mile to get to the Blue line to get there.

            Granted, going for a walk was part of the motivation, but still. I’d rather ride the train than try to find parking at MOA on the weekend (on the rare occasion I decide to go there), and it would have been much faster to drive.

    • John Bailey June 6, 2014 at 10:08 am #

      I won’t repeat what Adam said above about judging the Green Line on the downtown-to-downtown length which has only ever been projected to be around 5% of trips. Many more will be trips like my eventual ones from Fairview to one of the downtowns. The new estimated longer times probably only add 2-3 minutes on these trips.

      As to parking on University Avenue, let me preface by saying I think there should still be (well-managed, metered) parallel parking on University and a study is starting on that soon (but that’s another thread for another day). But I would strongly disagree that there is a dearth of off street parking on University. I live right off University and I’m always shocked at the abundance of surface parking lots scattered throughout the avenue to say nothing of the prevalence of curbside parking on the side streets. In a wold of differing legal authority and state law, I wish we could “combine” much of those lots into a shared parking facility and open up those lots for actual useful purposes, but alas, that will be tough nowadays unless you have seriously willing property owners. (And Big Daddy’s is the BBQ in the twin cities, in fact, I even wrote a blog about it and noted that there is parking behind the building: http://www.tcdailyplanet.net/blog/john-bailey/big-yum-big-daddys)

      And finally, yes, there were plans to bypass University entirely and just run the line down the median of 94. That would have undoubtedly gotten some kick-ass travel times. And it would have ignored most of the people that are going to use the line.

    • Bill Lindeke
      Bill Lindeke June 6, 2014 at 10:38 am #

      I’d be willing to bet a rack of ribs that Big Daddy’s will be around for a long time.

      (Long time = five years.)

      (Of course, if I lose the bet, there will be no ribs anyway.)

      Also, Saint Paul has been working on creating combined “shared” off-street parking lots on University. There’s a guy in Public Works (I think) whose spent a year focusing on it. But in my understanding, it’s very hard going as many business owners don’t want to cede their sense of parking as private property.

  2. Bill Lindeke
    Bill Lindeke June 6, 2014 at 9:50 am #

    “any fudge factor mostly gets eaten up”

    yum!

    PS, why the low speed limit on the Washington Avenue bridge?

    • Mike Hicks June 6, 2014 at 10:23 am #

      Dunno. I may also be misreading things. There are certainly a few glitches in my data.

  3. Anne White June 7, 2014 at 2:20 am #

    When the Stops4Us coalition was fighting to get the three missing stations built at Hamline, Victoria and Western, we were told by Mark Fuhrman at the Met Council that each additional stop would add 45 seconds to the trip to accommodate slow-down, boarding and getting up to speed again. If that was true, presumably each station along the line would add 45 seconds. This would eat up 15 minutes, 45 seconds for the 21 stops between the two downtowns, including stations shared with the Blue Line, but not counting the stops at each end. It does not appear that any of the end-to-end estimates we’ve heard recently allow for this much time at stops, but it would be interesting to hear from the Met Council engineers how much time they’re anticipating per stop based on the test runs, which of course do not include boarding passengers.

    • Adam Miller
      Adam Miller June 7, 2014 at 10:58 am #

      Trading speed for stops that people will actually use seems like a no brainer.

  4. David June 8, 2014 at 1:08 pm #

    1. DT Mpls Blue line now Green, why no signal coordination? esp. now w/ both lines passing thru same signals.
    2. casual observer living & working DT StP appears little or no there eitherl 3-car trains in some blocks when stopped for red light hang over back in intersection behind — sigs set right would speed up train, but cars too.
    3 – Univ Av should be one traffic lane w/ turn & bus stop lanes and parking restored in front of shops.

  5. Ryan Johnson
    Ryan Johnson June 11, 2014 at 1:01 pm #

    This is awesome! I’d love to see this sort of analysis for busses too: what if high frequency bus routes had control over signals and didn’t have to stop and wait so much? How much time could they shave off, or would it even matter?

    On the other hand, I’d really love it if we could kill the idea that the train is somehow falling short of being the fastest public transit option between the downtowns, rather than what it is: something that improves access, consistency, amount of riders, and speed for people living along the corridor, not just people going between the downtowns. For that downtown-to-downtown trip, there’s already an express route, which people should really want to take (and it’s fast!). Maybe MTC needs to make those busses seem fancier, advertise more at train stops or something, but as more people from Minneapolis “rediscover” downtown St. Paul as a destination, they’re going to want to get there faster.