APPLICATION & CONTEXT
On signalized streets with a high volume of transit vehicles, typically more than 10 per hour or with combined headways less than 4 to 6 minutes, in mixed-traffic or dedicated lanes.
Where active transit signal priority is less feasible or has limited benefits, including streets with short distances between signals, streets with high pedestrian activity levels, and streets with short signal cycles.
Transit signal progressions are highly effective on one-way streets. On two-way streets, it may be necessary to prioritize the peak direction transit service if progressions are not possible in both directions.
Reducing signal progression speeds to meet average transit running times allows buses and streetcars to keep up with the signal progression.
Especially on streets with transit lanes, or where most traffic clears within the vehicle platoon, transit vehicles can catch up to the signal progression after a stop.
The combination of a low-speed signal progression and short signal cycles can improve transit performance.
Timing signal progressions to lower speeds provides additional efficiency benefits to bicyclists, and promotes a safer urban street environment for all users by discouraging high speeds.
The combination of reduced variation and reduced average travel time by using transit signal progressions can result, over the course of a long, frequent transit route, in enough time savings to result in an additional run with the same number of vehicles.
To maximize the effect of passive signal priority, transit travel time variability should be reduced through stop consolidation and dedicated transit lanes.
Signal progression speeds should be considered in the overall context of the street. Block length, crossing distance, and traffic volume are relevant to the selection of transit-friendly signal progression speeds.
Private motor vehicle travel times may be increased when signal progression speeds are reduced, but since signal delay is a large portion of car travel time, short signal cycles may offset this increase for most trips.
On downtown streets with intersecting progressions or on transit corridor streets with high transit volumes, active transit signal priority can be impractical. Instead, signal timing can build typical dwell time at stops into the signal progression, or the progression can be set to a lower speed.
Include cross-street progressions in signal timing planning, especially for streets with high transit or total volume.
On streets with a mix of transit services, extra attention will be needed to set offsets to minimize delays. In some cases, signal timing changes will require prioritizing a rapid service over a local area.