Module D - Slide 21
These two images of a typical four-leg intersection show sequential phases of a split phased signal. In the image on the left, all vehicular traffic going north, turning left, right, and traveling straight through, will be moving as pedestrian going north on the east crosswalk (bottom right corner, southeast corner) will have the WALK indication. At that time a pedestrian on the west crosswalk traveling north (bottom left corner, from southwest corner) will have a DON'T WALK, since the northbound left turning traffic has a protected turn. Without APS, when a blind pedestrian on the bottom left corner (SW corner) hears the northbound through traffic, they might assume that they have the WALK indication because traffic is moving on the parallel street. If they attempt to make their crossing at that time, there is a potentially dangerous conflict with northbound left-turning traffic which has a protected turn arrow and does not expect pedestrians. The pedestrian on the west crosswalk is supposed to cross in the next phase, shown in the graphic on the right, when all the southbound traffic has a green signal. While many pedestrians who are blind have been taught to cross with traffic in the nearest lane, which would be the traffic coming toward them when they are crossing northbound from the SW corner, it can be difficult to sort out by listening. In addition, the often heavy turning movements can present a false cue for pedestrians crossing east and west. For example, when crossing from the SE corner, westbound, in the image on the right, the turning cars may be heard as a surge of eastbound traffic. Because of the high potential for confusion with split phasing, 6 points are given for that type of signalization.