Green Line Getting Up to Speed in Fits and Starts

Heading east from Minneapolis, the Westgate Station is the first Green Line port of call in Saint Paul. Trains stop in the shadow of the KSTP radio mast, out front of an apartment building with a ground floor Dunn Brothers Coffee, Metro PCS, and Snap Fitness.

Sometimes they also stop a little bit before they’re intended to.

Like many other stations on the Green Line, Westgate’s platforms are offset. This requires Green Line trains to pass through a cross-street immediately before pulling up at the platform to pick up passengers. Occasionally, the stoplight at the intersection is red for University Avenue traffic—and for the trains.

It can be a frustrating experience for riders. One of the great advantages of public transit is predictability. Another is avoiding the stopping and starting that urban drivers are all too familiar with. When the train is made to brake every couple blocks to wait at a red light, these benefits are erased. It’s equally frustrating to stand waiting on a platform for a stopped train that you can see and nearly touch but cannot board.

The road that splits the Westgate Station is called Berry Street, and it is an exceptionally egregious example of the problems that have plagued the Green Line this summer. Berry Street does not fully cross University—it is a three way intersection. It is one block long. Traffic is so low that the city has not bothered to do an actual count. KSTP employees and residents of an apartment complex are the only regular users of the street. In other words, barring an emergency, there is no reason a Green Line train should ever stop at Berry Street.

Yet, every day, many do.

BerryStreet

How many? Over the course of several days, this writer (who lives nearby) observed 100 trains pass through the Berry Street intersection, exactly 50 each way. All told, 32 trains were forced to come to a complete stop and an additional three slowed almost to the point of stopping. The length of the wait varied considerably. The average delay was about 17.5 seconds, but the longest delay ran nearly 50 seconds.

Per the Star Tribune, there are nineteen similar intersections along the Green Line. Back of the envelope estimate: if we extrapolate from Berry, trains are stopped at a third of all low traffic intersections for an average of 17.5 seconds. That adds nearly two minutes to all trips from the “low hanging fruit” intersections alone. That’s not including the effect of busier cross streets like Snelling, where riders can wait a minute or more, nor the time wasted simply by trains slowing down. Multiply by the average weekday ridership of the Green Line (again, back of the envelope) and that comes out to over 1,100 hours lost, per day. In less abstract terms, Green Line delays inevitably result in missed connections and a lot of waiting on platforms (which will sap energy and patience in the winter).

Ever since the June 14th opening, it has been clear that red lights are one of the most pressing issues facing the Green Line. These intersections should be low hanging fruit for the city to fix. It’s surprising that these delays existed at launch at all.

Changes are coming, although not as quickly as one would hope for.

“Predictive priority has been implemented at several low-volume intersections along University Avenue,” wrote Drew Kerr, Public Relations Specialist with Metro Transit, in an email conversation. “We expect predictive priority to be implemented at [the rest of the low traffic intersections] over the next several weeks.”

Predictive priority is the name of the system that identifies approaching trains and attempts to time the traffic light to let the train pass without stopping. It is not the full preëmption that Aaron Isaacs argued for in his earlier post on this blog, but it appears to be working well. This writer observed several hours of train crossings at Pascal St., which was one of the initial group of intersections that tested the priority system. Only one in every six trains noticeably slowed their speed, and none were made to come to a complete stop.

As of this writing, predictive priority has been implemented at ten intersections in Saint Paul: Park, Western, Mackubin, Grotto, Victoria, Chatsworth, Griggs, Pascal, Aldine and Fry. In addition, Marion St. has also been given an advanced detection system. The fixes are moving westward in Saint Paul, presumably with Berry Street the last to be addressed.

“With successful implementation of predictive priority (note: so far) end-to-end Green Line trips are now averaging approximately 52 minutes westbound and 50 minutes eastbound,” said Kerr. “Trip times have also become more consistent.”

Metro Transit is also looking at implementing the same system for busier, medium-traffic intersections. However, giving the Green Line a measure of priority over the most highly trafficked intersections is not currently in the plan. Instead, Metro Transit hopes that in fixing the majority of intersections the waits at the remainder will straighten themselves out. Every intersection where the train may or may not stop is a variable that makes predicting where the train will be at any given time more difficult. By eliminating as many variables as possible, it will be easier to predict the train’s arrival at several key intersections.

While the work on streamlining the Green Line’s route is not yet done, it’s clear we are near something like a finished product. The train may soon complete its trips in the 48 minutes that was originally promised. “Metro Transit is pleased with the progress that has been made since predictive priority was introduced,” said Kerr. “[We] look forward to continued success as the technology is implemented.”

Better late than never.