Took a mini-road trip over the past few days and saw some interesting signal configurations:
Meredith NH: I noticed some preemption equipment at this PHB signal. There is also similar equipment in Quincy MA as well. How does preemption work with these signals? Does it simply inhibit the pedestrian phase and/or terminate an in-progress pedestrian phase?
Chelsea MA: This 3-section traffic signal for a right turn slip lane is R-Y-FR, near a drawbridge. Never seen this configuration before and it looks more like a fire signal that you'd normally see on the fire station side and/or side streets.
Regarding preemption, it is likely that those HAWK signals get preempted by delaying the pedestrian call. That is the only phase that would affect emergency vehicles. If the signal is dark, it should stay dark longer. If it is already flashing yellow, it can flash yellow a little longer. Once it goes to solid yellow or solid red it has to remain on that, because a pedestrian will be crossing. A flashing red also cannot be terminated early, as that is part of the pedestrian clearance phase. (but then again, traffic can proceed on that phase with a stop)
Correct me if I'm wrong, but if a pedestrian call has been activated, I believe that preemption cannot shorten the pedestrian clearance phase, i.e. the flashing don't walk. But pedestrian clearance can bring the signal from walk directly to the flashing don't walk phase.
I don't understand the R-Y-FR signal for a drawbridge. Perhaps they allow a flashing red when the signal opposes cross traffic so that turning traffic will come to a complete stop and yield to any traffic in its way, but a solid red is shown when the drawbridge is up. IMO, something like this would be better served with a regular R-Y-G signal and then an electronic no right turn sign that lights up when the bridge is out. This is common at many right turns where the road you are turning from is parallel to a RR crossing.
Los Angeles has a unique application of this type of signal at driveways that are part of a regular intersection, signalled as R-FR-Y. When I was a kid, these were signaled with a R-FR, but now they have added a yellow phase as well.
Take a look here:
https://www.google.com/maps/@34.0551703,-118.3863072,3a,75y,215.66h,86.18t/data=!3m6!1e1!3m4!1sgDfPl-XyfEivPNanRbJ5Mg!2e0!7i16384!8i8192Basically, Livonia is a small street that ends at Pico at a T-intersection. But it's not a pure T, as from the top of the T is a driveway to/from the bank parking lot. In this manner, a left from Livonia to Pico is given right of way over traffic from the bank heading down Livonia. When Livionia gets green, bank gets a flashing red and sees a sign to "watch opposing traffic". Since its a flashing red, the driveway traffic is forced to treat the intersection like a stop sign, even though the main Pico traffic is stopped by a red light.
While something like this may be useful over a small driveway, I don't like the arrangement here. THe normal traffic pattern should be that both directions get green and that anyone turning left must yield to opposing traffic.
