Traffic signal pre-emption failure.

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At the intersection of Harvard and Washington Avenue, adjacent to the University of Minnesota campus, there is a safety problem with traffic signal pre-emption, described below. I reported this to the University of Minnesota Transportation and Parking, whom I am sure dutifully passed this up the line. However, I looked online to figure out who to report to directly, it is not obvious.

I go to MnDOT's page which says:

Question: I know of a traffic signal that has indications out or appears to be malfunctioning. Who do I contact?

Answer: First, you need to know which government agency owns and operates the traffic signal (city, county or MN/DOT). Generally, if a state highway has an approach to the traffic signal, then MN/DOT is likely to operate the signal. If no state highway is present, only county or city roads approach the signal, then the county in which the signal is located is likely to operate the signal. If no state highway or county road is present at the signal, only city streets approach the signal, then it is likely that the city in which the signal is located will operate the signal. Once the operation and ownership of the signal is determined, you can contact the agencies [sic] Traffic Engineering/Public Works department. Click here

Now if you "Click Here", you would expect to see who owns which signals. E.g., one would hope to see a map, I could click on the intersection in question, and it would tell me who owned the signal. The best I get is a list of counties and cities. Well even if I know which county and city I am in, (and I do, but I suspect most U of Mn students are only vaguely aware of the existence of Hennepin County) I still don't know who owns the signal, and the links are just to the county and city websites, not the traffic engineering groups. I think Washington Avenue is a city rather than county road, though the Washington Avenue bridge is a county facility. My next step is calling 311, so I hope that gets through (my confidence level is low).

Now the problem:

The design of a traffic signal pre-emption for emergency vehicles is supposed to save emergency vehicles time, by turning a red light green, subject to constraints. Typical verbiage is

• A green light is not guaranteed. Emergency vehicle drivers need to use caution not to over-rely on the system and need to be prepared to stop if provision of the preemption phase is delayed (i.e., awaiting time out of an in-progress pedestrian phase). Emergency vehicle preemption operation and limitations must be a part of initial and recurring emergency vehicle driver training.

Similarly New Jersey requires

If pre-emption is approved, a timing sequence needs to be developed that provides adequate time to allow for safe egress of the fire/rescue vehicles. Care should be taken to ensure that all timing plans have a sufficient guaranteed minimum green time to the main street to avoid the display of a “flash” green. All vehicular and pedestrian clearances times must be guaranteed.

The problem is that the in-progress pedestrian phase at this location is not in fact given time to clear. I was walking NB on the sidewalk adjacent to Harvard Ave. at the intersection with Washington (Thursday, Nov 18 about 12:30). The pedestrian phase gave me a walking man indicator. I and others began to cross. The phase should be at least 12 seconds (4 lanes at 12 ft each, at a human walking speed of 3 ft. per second). It normally is. However speeding along Washington Ave EB is an emergency vehicle with lights and siren blaring. The light immediately (say about 2 seconds into the ped phase) changes from green to red (red to green on Washington). The pedestrians have now been stranded, since unlike vehicles, they cannot clear the intersection in 2 seconds. So I and others are now on a pedestrian crosswalk, which we entered legally with the light, while cars on Washington think they have a green light, and being cars driven by drivers, and being treated like idiots, behaving like idiots proceed to go, trusting the traffic light rather than observing conditions around them (like the mass of pedestrians in the crosswalk). Even if the pedestrian were there illegally, the car would not be legally allowed to hit them.

Were this the only problem at this intersection, I would just assume I missed something. In fact this is the second problem I have observed and reported in just over a week. On Nov. 10 just before 1:30 I observed that the light was mishandling pre-emption, in this case I think it was transit pre-emption. Basically the pedestrian phase (on the north side of Washington) went from "hand" to "flash" and then back to "hand", as a bus was coming through (hence my thought it is related to signal pre-emption, buses pre-empting the gap-out or max-out condition). The queue on Harvard was quite long, and the pedestrians were backed up at the signal (I pushed the actuator several times, but it didn't seem to come through).

1 Comment

Reminds me of an incident last summer. I was at a stop light and noticed it wasn't changing for anybody. About a block over was a parked firetruck with the lights blinking. Kind of makes me wish there was a maximum sensitivity time to the light pre-emption, something like 5 minutes.

David Levinson

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This page contains a single entry by David Levinson published on November 20, 2010 10:04 AM.

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