(05-17-2017, 12:05 AM)timc Wrote: How effective are the priority signal units? I think it's a good idea.
The units themselves can be quite effective, but it's a question of how they're configured. The units can be configured for absolute pre-emption (signal immediately changes) which is what ambulances/etc get, but obviously that would be too far. Currently GRT has signal priority on route 200 and it's configured to allow extending green/yellow times by a few seconds but only when the bus is behind schedule, the light hasn't recently been extended by a bus, and only at a small number of designated intersections. And the buses are scheduled such that they should never be behind schedule in normal traffic, so the units are mostly unused.
It would be more interesting if GRT started tightening the schedule enough that signal priority was required to keep the schedule, and the units were actually regularly used. Also if the amount of adjustment was allowed to exceed a couple seconds, and to be used repeatedly at the same intersection. But I've seen no sign traffic engineering is willing to let them do that, and it appears they're not even willing to let ION do that. So we'll have to wait and see what the actual effect is.