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Field Adjustments

Effect of Signalization Changes

Pedestrian actuation
Pedestrian actuation requires the blind pedestrian to locate and push a pushbutton, then cross on the next pedestrian phase, to be assured of having enough time. Blind pedestrians have two types of problems at these locations:
  • They have traditionally waited through a light cycle to assess and refine their heading by listening to vehicular trajectories, before crossing at the next pedestrian phase. At a pedestrian actuated intersection, that is not possible because blind pedestrians then have to locate and push the button again (and re-establish their heading).
  • At a location with little vehicular traffic, even if pedestrians who are blind know there is a pushbutton and use it, they may not be able to detect the onset of the Walk interval if there is not a vehicle traveling straight ahead on the street parallel to their crossing.
Vehicular actuation
Vehicular actuation allows the cycle to skip phases, so pedestrians with visual impairments cannot accurately predict when in the cycle the pedestrian phase will begin. Right-turn-on-red makes it harder to determine the surge of traffic at the onset of vehicular green on the street parallel to the crossing direction. Blind travelers must wait to hear a car traveling straight across the intersection to determine that the light has changed, so they frequently are delayed in initiating crossings while they determine that parallel traffic flow has begun.

In addition, some locations do not include a pedestrian phase, and at times when vehicular volume is low, there may not be enough time to cross the street.

Exclusive pedestrian phase
Exclusive pedestrian phases eliminate the traffic surge concurrent with the onset of the Walk interval, thus removing the most reliable cue to the onset of the Walk interval; exclusive pedestrian phases where right turn on red is permitted may never sound to blind pedestrians like they have a Walk interval.

Exclusive pedestrian phases eliminate traffic parallel to the pedestrian's crossing direction, thus making it more likely that serious veering will occur.

Leading pedestrian interval
Leading pedestrian intervals are undetectable to pedestrians who are visually impaired; by the time they hear concurrent parallel traffic and initiate a crossing, not only will they have minimal crossing time, but also drivers will not be expecting them to initiate a crossing.

Split phase timing
Where there is split phase timing, the surge of left turning cars may be mistaken by blind pedestrians as indicating the onset of the Walk interval and blind pedestrians may cross into the paths of left turning vehicles.

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