Transit Signal Priority – A driver’s perspective
Choose Your Way Bellevue has an interview on their site with John Toone, the Intelligent Transportation Systems (ITS) program manager at King County Metro. John discusses Transit Signal Priority as well as other signal enhancements along the B line – It’s worth a look.
When the RapidRide B line started up in October, signal priority was still not active. As I drove the route I’d frequently get stuck at red lights, hardly an unusual experience when driving a bus. Over the subsequent weeks, as signal priority has been turned on, I’ve noticed the effects of signal priority. In more and more cases “stale green” lights, which Metro trains us to watch for and be prepared to stop at, would stay green long enough to let me catch the light. I actually found this transition a bit disorienting since I usually approach most stale green lights intent on stopping. With TSP active, I find myself making far more lights so I’ve modified the way I approach these “stale green” lights. I keep a bit more speed coming into the lights I expect to stay green but still low enough that I can safely stop. (As John told me in an email, it’s signal priority not preemption, so I’m not always guaranteed a green light)
After speaking with Metro planners, I’ve learned that most of the signals along the B line that were scheduled to have TSP are up and running. Despite that, there is still some tuning to be done. On a recent series of trips, my coach was detected anywhere from 19-25 times out of 33 currently active prioritized intersections. Apparently, there are still some adjustments to be made to the wireless system along the route to detect the coaches. I’m told the work is ongoing and that I should see further improvements over the coming month.
There are also some intersections that don’t have TSP, which I approach the old fashioned way – foot hovering above the brake and accelerator ready to smoothly stop. (I strongly suspect NE 24th St & 152nd Ave NE and NE 40th & 156th Ave NE in Redmond are without TSP. If I’m wrong, then they need tuning 😉 I’m working hard to be patient since I can only imagine the ripple effects of giving too much priority to my bus. I try to picture my bus cutting a rough line through a gently rippling pond. The trick for the traffic planners is to make that cut as smooth as possible and not disrupt the other ripples too much.
I’ll add future updates as I hear about or see further changes. In short, while signal priority will never be a substitute for dedicated right of way, it is already making improvements in travel time for RapidRide. As the kinks continue to get worked out, I look forward to seeing even more improvements.
NOTE: Since I drive RapidRide in the morning, my experience is relatively limited. I’m sure the afternoon trips, with their much heavier traffic, are a bigger test for the system. Keep that in mind when drawing any conclusions from reading my impressions. I’m looking for a vacation relief assignment on RapidRide in the afternoon to drive but so far I haven’t seen one.