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9 Table 5. Midblock crossing speeds of pedestrians with and without walking difficulty. (9) Average Standard 15th 50th 85th Speed, ft/s Deviation, Percentile, Percentile, Percentile, (m/s) ft/s (m/s) ft/s (m/s) ft/s (m/s) ft/s (m/s) Pedestrians with Walking 4.23 0.28 3.28 4.30 4.99 Difficulty (1.29) (0.09) (1.00) (1.31) (1.52) Pedestrians without Walking 4.75 0.22 4.04 4.72 5.45 Difficulty (1.45) (0.07) (1.23) (1.44) (1.66) All Pedestrians 4.66 0.24 3.87 4.66 5.41 (1.42) (0.07) (1.18) (1.42) (1.65) average crossing speed to be 4.7 ft/s (1.4 m/s) and the 15th per- Varying Speeds During a Crossing centile speed to be 4.0 ft/s (1.2 m/s), very close to the general One Australian study (15) concluded that pedestrian design speed of 4.0 ft/s (1.2 m/s) recommended by Australian speeds for the first half of the crossing were higher than and U.S. design guides. speeds in the second half, and the average and 15th percentile crossing speeds decrease with increased pedestrian flow rate. Also, crossing speeds and characteristics were similar during Pedestrian Start Loss and Clearance the weekdays and weekends. Time Gain Calculating start loss time and clearance time gain are Pedestrian Space important in determining a pedestrian's effective green time, Requirements which is needed to model pedestrian performance measures (e.g., delay, queue length, and number of stops) (9). Start loss A recent study of pedestrian characteristics (16) recom- time is the time lag for stepping on the crossing after the Walk mends for standing area design a simplified body ellipse of display begins. Clearance time gain is measured as the first 19.7 in by 23.6 in (50 cm by 60 cm), with a total area of 3.2 ft2 part of the pedestrian clearance (Flashing Don't Walk) inter- (0.3 m2), or roughly 108 percent of the ellipse suggested by val when the pedestrian continues to step on and use the Fruin's 1971 study (17). This shape (see Figure 1) serves as an crossing (9). Table 6 summarizes pedestrian start loss and approximate equivalent to Fruin's ellipse. This study also rec- clearance time gain values for both intersection and midblock ommends a body buffer zone of 8.6 ft2 (0.8 m2) for walking, signalized crossing sites and shows similar findings to Table 3 near the upper end of the buffer zone range provided by in that start loss values are larger for intersection signalized Pushkarev and Zupan (18) and just before "unnatural shuf- crossings (possibly due, again, to a perception of a less safe fling" commences. environment) (9). Washington State's Pedestrian Facilities Guidebook (4) states Another study of pedestrians at midblock signalized cross- that two people walking side by side or passing each other while ing sites only found the average start loss to be 1.3 s and the traveling in opposite directions take up an average space of 4.7 average clearance time gain to be 2.9 s, pedestrian movement ft (1.4 m) with adequate buffer areas on either side (see Figures parameters close to the default values used in the SIDRA 1 2 and 3). The minimum width that best serves two pedestrians software program (1 s and 3 s, respectively) (15). walking together or passing each other is 6 ft (1.8 m). Table 6. Comparison of pedestrian movement start loss and clearance time gain values for intersection and midblock signalized crossing sites. (9) Start Loss Clearance Time Gain Clearance Time Average, s Standard Average, s Standard Gain Less Start Deviation Deviation Loss, s Intersection Signalized Crossing Sites All Weekdays Combined 2.79 1.57 2.84 2.64 0.05 All Weekends Combined 2.57 1.45 2.05 1.43 -0.52 All Sites Combined 2.68 1.51 3.02 2.31 0.35 Midblock Signalized Crossing Sites All Weekdays Combined 1.35 0.57 2.75 2.38 1.40 All Weekends Combined 1.27 0.53 3.08 2.17 1.80 All Sites Combined 1.30 0.55 2.93 2.25 1.60
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10 19.7 in (50 cm) Body Depth 23.6 in (60 cm) Shoulder Breadth Figure 1. Recommended pedestrian body ellipse dimensions for standing area (16). 12.7 ft (3.9 m) 8.7 ft (2.6 m) 4.7 ft (1.4 m) Figure 2. Spatial dimensions for pedestrians (4). Figure 3. Spatial needs for pedestrians with Spatial Bubbles volume changes (4). A spatial bubble is the preferred distance of unobstructed forward vision while walking under various circumstances Pedestrians with Disabilities (4). Figure 4 illustrates the special bubbles that are comfort- able for the average pedestrian while attending a public event, Space requirements for pedestrians with disabilities vary shopping, walking under normal conditions, and walking for considerably depending on their physical ability and the pleasure. assistive devices they use. Spaces designed to accommodate Figure 4. Forward clear space needed by pedestrians (4).