Over the past week, the SDOT blog illustrated the concept that all pedestrian treatments at signals are not universal. We are committed to choosing the right treatment for the right place in order to have both safe and efficient operation for all transit modes. We also discussed that SDOT is working on new guidelines to help our engineers decided which treatment to use where. You may be asking yourself what treatments can we do at intersections?
Crosswalk light at Meridian Ave N and N 105th St
Below is a list we developed of different types of signal timing treatments at intersections. Some of these are stand-alone treatments and some can be combined with others. This list is not fully exhaustive as we also have an inventory of over 1100 signals where we have existing treatments that we try not to use as we revise signal timing and overall operation.
Disclaimer: This gets very transportation nerdy.
Walk Times
Slower walk speed for flashing don’t walk calculation.
The standard calculation currently uses a 3.5 feet per second walk speed which changed in 2009.
Longer walk time by request
This allows the pedestrian to push and hold the push button and request a longer walk time than usual. We’ve only tried this at one location so far Elliot and Roy.
Time of day walk times
This allows the engineer to program different walk times for different parts of the day. In some locations, like adaptive corridors, the signal chooses different cycle lengths depending on traffic volumes. In these locations programming different walk times for those cycle lengths is critical.
All-walk at Broadway and Denny
Separate Phases
All-Way Walk
This treatment programs all the walk phases to come on at the same time and is timed to allow for someone to make the diagonal crossing.
All Walk
This treatment programs all the walk phases to come on at the same time and is not timed to allow for someone to make the diagonal crossing.
Leading Pedestrian Interval
This treatment gives pedestrians a 3 to 5 second head start on compatible vehicle phases in order for the pedestrian to be fully visible in the crosswalk.
Delayed Walk
This treatment gives vehicles a 3 to 5 second head start on compatible pedestrian phases in order to clear vehicle traffic and reduce potential conflicts.
Right Turn Overlap
This treatment services right turn phases during compatible movements in order to clear vehicle traffic and reduce potential conflicts.
Turn Restrictions
This treatment limits turning by vehicles in order to reduce potential conflicts.
Protected Turns
This treatment creates separate phases for pedestrian movements and turns in order to reduce conflicts.
Leading Turns
This treatment brings up protected turns at the beginning of a cycle in order to clear vehicle traffic and reduce potential conflicts.
Lagging Turns
This treatment brings up protected turns at the end of a cycle.
Compatible Walks with Special Phase
This treatment reservices pedestrian phases during special phases like transit queue jumps or compatible turn movements.
Protected Walk
This treatment uses a flashing yellow arrow for left turns when no pedestrian is detected and a protect only turn when pedestrians are detected.
Pedestrian Overlap*
This treatment reservices pedestrian during compatible movements.
Detection Methods
Passive Detection*
This treatment detects pedestrian presence at an intersection without the pedestrian having to do anything.
Vehicle Call = Ped Call
This treatment puts in a request for a pedestrian phase any time a compatible vehicle phase is requested.
Pedestrian Recall
This treatment puts in a request for a pedestrian phase on every cycle.
Dual Coord Phase
This treatment puts in a request for all phases on every cycle.
Cycle Lengths
Lower Cycle Lengths
This treatment lowers the amount of time you have to wait between walk phases at any given crosswalk at an intersection.
Half Cycles
This treatment provides more opportunities to cross by lowering cycle lengths at minor intersections on a corridor while still providing progression for the main road at the intersection.
Late Arrival
Pedestrian Reservice*
This treatment reservices pedestrians after the green for the compatible vehicle phase has already started.
Late Call*
This treatment creates a bigger window for pedestrians to request a pedestrian phase before moving to the next phase in the cycle.
*These treatments are not currently available in our signal software but we are working with our manufacturer on prioritizing these elements. So stay tuned! Next time, we’ll discuss the pro’s and con’s of these treatments!