MPR Decoder: Green Line Signal Timing

Occasionally, I listen to Minnesota Public Radio. So, occasionally, I share with you what I have heard in a segment I call MPR Decoder.

Here's last week's short Daily Circuit segment about signal timing on the Green Line. Host Tom Weber had on Brian Lamb from Metro Transit and Nancy Homans from the Saint Paul Mayor's Office to talk about the tension between the city and the Met Council over the stoplights of Saint Paul. Both officials stayed on message pretty well, even when Tom dropped a Chuck Marohn soundbyte on them (which the transportation policy equivalent of a bunker buster bomb). 

You can listen to it here, or enjoy this rough [slightly annotated] transcript:


Tom Weber (TW): ... to the amateur observer [i.e. everyone with half a brain], it would seem a quirk makes this trip longer. It might be too late to change, but give us the theory... Why is it that stations were put after that stoplight vs. before, and now there are situations where there are two stops?

Brian Lamb (BL): When you’re taking the width of the street and trying to split the stations, if they were side by side it would further curtail the driving lanes ["curtail" is an interesting verb], so that’s why we have split stops.

TW: You have em right now where the stations are across the stoplights. But why not switch it? Why not have it be before the red lights, so that you’re putting the stops before the red light?

BL: Technically we do have the capability to reverse run [I like anytime a wonky professional drops jargon, like the "reverse run"], so we could run the westbound train down the eastbound tracks. However the system is designed that when we get the signalization optimized, and we don’t have it done quite yet [understatement], the train will go right through the intersection and only stop once. So therefore then it has a little more dwell time that's possible, on the far side before it leaves for the next station.

TW: So if it were before the stoplight and it turned green but the operator was loading passengers the train operator might feel pressure to say, c’mon!

BL: Exactly. You might miss another 90 seconds of the signal.

TW: So Nancy, the city has a big role here because the Green Line itself are operated by Metro Transit, but the lights are operated by the city. It sounds like its not working quite yet.

Nancy Homans (NH): We knew that from the get go, that once the system was installed it would take some fine tuning. It has to serve obviously automobile drivers, bus riders, pedestrians, bicyclists, folks who want to cross the intersection. [And in that order, too.] We made a commitment from the get go that the Green Line would not be a wall down the avenue that people would be able cross to get to the stores on the other side. So the challenge is that everybody gets the amount of time they need and everybody is well served and we are making those adjustments.

TW: The city … one of the debates is about "minor intersections" that the city could give up a little bit of its power to operate those lights and hand it over to metro transit so that it flows better. Is that gonna happen?

NH: What the Met Council and Metro Transit have asked is for us to consider signal preemption, which is that if the train is is coming it gets priority, at these intersections. We have indicated that we are willing to do that. [The "we have indicated that" is such a passive super political speak kind of phrase, isn't it. Like, "we have indicated we'll help you using a secret code akin to baseball signs where the managers scratch themselves on the ear..."] We need a little bit more comfort around some detection systems, but we are wiling to do that because we believe that if we can shave off a little time of those intersections, that the Snellings will work better. [“The Snellings" is like a nightmare I keep having, where I'm stalked by evil MnDOT engineers or something. Or maybe it's a horrible disease? "Looks like you've got a case of the Snellings. That's not going to clear up anytime soon."] 

But the challenge is that those intersections are green all the time unless someone has pushed the walk button to cross, or there’s someone waiting to cross [in a car]. So how those people are served or how a pedestrian is served... we want to make sure that those people aren’t skipped where they’re waiting and then wait for a train and then there’s a full 90 seconds or so before they get to cross. So we’re just trying to make sure we get that right.

TW: Is the goal and the meaning of the line to get people from downtown to downtown quickly? Is that actually the goal?

BL: As with many forms of transit, it has multiple goals. There are fewer people who will go the full length of the route from downtown to downtown, than people who... maybe the average length is a couple of miles... to go to a different part of the corridor. And that’s what makes this route so successful. 

By the way, we’re already over 30,000 riders per day, which is one of the most successful new starts in the country over the last several years, because it has that intermediate traffic. [More successful than the great Peoria express bus of 2011!] So it really has to serve people going long distances and those going short distances. 

For the most part those going downtown to downtown during peak they also have the option of the 94 express service. That bus is very successful as well.

TW: The solution sounds like you’re not saying "oops we made a mistake when we made the stations," [Britney Spears song?] but you’re saying that you’re saying you can fix what’s going on now simply by altering traffic signals. Is that correct?

BL: That is correct. We believe that with the proper signal balance b/w preemption and priority which is just the signal timing that we can keep the trains moving so that the only times the trains are stopped is when they’re picking up people. 

TW: So Nancy when will that happen?

NH: [She's not gonna answer that one!] We have a team of folks that are working on an intersection by intersection basis. So we will see improvement over time. We’ve already seen improvement from June 14th to today. And we expect to be working on this for months. And when new development and new transit are added we’re going to have to tweak it again. This is a continuous process of getting this right and we believe that when the signal timing is improved that will improve the ability of operators to predict that the lines going to stay green and they’ll be more confident going through the intersection. 

BL: And it is an iterative process as the signals get more synchronized we believe we can pick up the travel speed b/w the two stations and then it’ll cause another round of signal optimization. We’re at 33K before the U of MN or any other colleges are really in session, as the loads start to change that’ll be another opportunity to tweak the schedules.

TW: Nancy said we’re not gonna just make a wall and that the LRT is just going to go through untouched, its one of the things debated. Last month we spoke about transportation funding. Here's a short piece of audio from Chuck Marohn, of the organization Strong Towns... [Dropping a clip like this must be the best part of a radio host's job!]

Chuck Marohn (on tape): ... a billion dollar investment, yet we make it stop at red lights, how can you have a billion dollars dropped on a line and say "we’re going to make it sit here and let that cycle through when there’s no other cars around or there’s one or two other cars on a side street getting across…" If you’re going to make an investment of that size why would you not make it the priority of the corridor well the reason is that we’re sensitive to the notion of shaping behavior, telling people how we’re going to live. Well, we’ve done that. We’ve spent a billion dollars on this corridor, and I think we’ve gotta own the fact that transportation does shape behavior.

TW: Chuck is saying, "own it." You spent so much money, you should make it the only thing going through all the time, thoughts?

NH: We also added three additional stations so we could serve the communities that live along the line, that they were the people that needed to get to education and employment and stop for them. [Classic dodge, like a Dodge Aires or something.]

TW: That’s not the issue that chuck was saying. Chuck was saying, fine have as many stations as you want but just get ride of red lights. [Well done, Tom. Asking the follow-up question after a dodge must be the best part of a radio host's job. Actually there seem to be lots of fun parts to a radio host's job. I'm probably wrong about this.]

NH: In order to allow peds to cross University safely, we needed additional signals. We added those. As part of the design we involved thousands of people to help us understand how to do this best. 

But we agree, we need to get through more quickly and we are going to work day in and day out to reduce those signal impacts on the train, and give the pedestrian the appropriate amount of time, but at a different time and space to get through. We need to get the train down University Avenue and support all the amazing development that’s happening along the line, the 30,000 folks that are already riding, and the people that will be riding.  We understand our responsibility to that [with great traffic FUBAR comes great responsibility], and we think we’re working a very fine balance and we have partners at Metro Transit to help us get that balance right.

[Sounds good to me. Let's get it done, Saint Paul! The proof is in the train.]

1 comment:

Benjamin Ross said...

we want to make sure that those people aren’t skipped where they’re waiting and then wait for a train and then there’s a full 90 seconds or so before they get to cross.

Isn't this exactly what traffic engineers do purposefully when they mark crosswalks on only 3 legs of a signalized intersection? Heaven forfend that a driver should be treated the way we routinely treat pedestrians!