We were curious about the Traffic Signal Priority system being touted as a benefit of the new RapidRideB service, so we took our questions to John Toone, the ITS program manager at King County Metro. John regularly works to expand and extend the capabilities of the ITS architecture of the transportation agency, As program manager, his duties range widely from policy and planning to installation and operation, and he was instrumental in getting the TSP system in place. Our conversation is below:
CYWB: What exactly is Traffic Signal Priority and where is it being implemented?
John: TSP is simply the idea of giving special treatment to transit vehicles at signalized intersections. Since transit vehicles can hold many people, giving priority to transit can potentially increase the person throughput of an intersection. TSP is currently active for RapidRide buses at all but three intersections on the B Line, which will come online as construction in Bellevue finishes.
CYWB: Could you describe how the technology works to a layperson, like ourselves, and explain why we should be excited about it?
John: TSP is part of our Intelligent Transportation Systems (ITS) architecture where the buses, roadside and central systems are all connected via a single network. The buses know their location using GPS and other technologies. When it reaches a defined point on their trip, the bus sends a wireless message with about 25 pieces of information to a device on the roadside. This device generates a request to the signal controller if the criteria set by Metro and the City are met. TSP doesn’t just make the trip faster, it’s also more reliable. So, buses come more regularly, get to their destination faster, and it costs less for Metro to provide service.
CYWB: How can you tell (as a rider) when it’s in effect?
John: TSP is a priority treatment, not a preempt, so a rider or driver won’t really notice an obvious change happening at the signal as with an emergency vehicle. The green light is held a little longer or the wait at the red light is shortened for the bus, but the lights will never change order. People get to know the patterns of familiar intersections, so if they get the feeling a light has been green for longer than expected, look around for a bus. In general, though, it’s hard to know for certain that a bus got priority at a specific light without looking into the system logs. But over a trip a rider will notice that the bus spends less time stopped at lights than a car.
CYWB: Will we see its use expanding to other routes as well?
John: TSP is a core feature of RapidRide, so the A Line and all future lines (we currently have plans for 6 total) will have this technology. Every bus in the fleet is equipped with the same on-board equipment as the RapidRide coaches so this could be expanded to other bus corridors as well, although there is no budgeted project to do so at this time.
CYWB: Can you name any “TSP success stories”?
John: On the A Line one less bus was needed than was initially scheduled to provide service due to the success of TSP and other priority treatments.
CYWB: What is the relationship (if any) between TSP and the new SCATS system being implemented in Bellevue??
John: SCATS is a very cool new generation signal control system that’s very smart and uses a lot of information inputs to adapt to traffic conditions. The first SCATS intersections with TSP are currently planned to be installed in January/February 2012 at 120th/NE 8th and 124th/NE 8th. With their integration, our system can be considered one of the inputs to their adaptation. As you probably know, modern thinking about traffic management is that the infrastructure is intended to move people and freight, not vehicles. SCATS can be much more successful about moving people by knowing which vehicles are buses full of them. We should be able to be more aggressive in how long we could hold a green light for a bus, as we have confidence SCATS can compensate quickly for those movements that were delayed a little more.
CYWB: At Metro, are you working on any technology-related projects besides traffic signaling that could potentially make bus rides go faster?
John: As I mentioned above TSP is just one part of our ITS architecture. This architecture includes the next bus arrival signs and ORCA card readers located at the RapidRide stations on what we call the “Tech Pylons”. Paying your fare while you’re waiting for the next bus is a great way to get on board and on the road faster. We designed the architecture so that new technology systems can be more easily integrated, which is one of the reasons it was nominated for this year’s ‘Best of ITS’ award that will be announced soon!