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Sub-problem 2a - Page 1 of 2

ID# C502A01

Sub-problem 2a: Analyzing the Effects of Pedestrians

Step 1. Setup

Because of the large number of pedestrians at this intersection, we might want to consider an exclusive pedestrian phase. We have resolved part of the pedestrian conflicts with vehicles by closing the northbound approach to vehicular traffic in Problem 1. However, the northeast movement of pedestrians from parking to classes suggests a diagonal crossing might be worth some consideration.

Assuming we need to maintain the 120-second cycle, we need to compute the pedestrian green time for the diagonal movement crossing. Using a crossing distance of 50 feet, a crosswalk width of 10 feet and a 4-feet-per-second walk speed, the minimum pedestrian time is calculated to be about 20 seconds. This assumes 500 pedestrians in thirty 120-second cycles per hour, or 17 per interval in the following formula from HCM Equation 16-2:

Incorporating this value into an exclusive pedestrian phase yields the following timing for the intersection:




G = 73 sec G = 17 sec G = 20 sec
Y = 4 sec Y = 4 sec Y = 0 sec
R = 1 sec R = 1 sec R = 0 sec

Take a few minutes to review the phasing plan with the exclusive pedestrian phase. By moving the pedestrians to their own phase, will they be assigned more or less time than they were before? What benefits are derived by assigning pedestrians with an exclusive phase? Click continue when you are ready to proceed.

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