Module D - Slide 20


The following variables are those that pertain to the intersection as a whole.

First variable on the form is Configuration. This pertains to the layout of the intersection. The choices are 4-leg (0 points), 4 leg offset (3 points), 3 leg T or Y (3 points), 5 or more legs (12 points) and midblock location (14 points). 4-leg intersections are the most common and easiest to predict and easiest to hear and use traffic sounds for determining when the signal changes. Other configurations present more unknown intersection geometry and sometimes a lack of parallel traffic noise. For example, a midblock crossing gets the highest point score mainly because it has no parallel traffic so there's no audible cue of when to cross.

The second overall intersection factor is signalization. The choices there are pretimed, actuated, split phase, and exclusive pedestrian phase. In this one again, the scores go up as the signalization becomes more complex or harder to determine by listening. For example, at a pre-timed signal, a blind pedestrian can listen to several cycles and learn the pattern of the signal (which will not change). At actuated signals, the cycle and phases are unpredictable, since they might change depending on traffic volume or time of day. This can be more difficult for a blind pedestrian. Spilt phasing and exclusive ped phasing are illustrated in the next slides