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14 Older Pedestrians Pedestrian Delay The experiences of older pedestrians differ from those of Depending on the research, pedestrian delay can have dif- the young. In general, older pedestrians do not behave as irra- ferent definitions. Most of the studies reviewed defined tionally as do many children and young adults. However, older delay as the amount of time between the point at which a pedestrians often have physical conditions that limit their abil- pedestrian arrives at the curbside and the point at which he ities to accurately assess the traffic situation. Older people also or she steps off the curb as well as any time that the pedes- tend to walk more than others because they have more free trian has to wait in the roadway for acceptable gaps in the time, and walking is good exercise and an inexpensive way to traffic. One major difficulty with this definition is deter- make short trips. The elderly are more law abiding than the mining when a pedestrian "arrives" at the curbside. For general population, and they may, in fact, be too trusting of instance, a pedestrian may walk straight to the curb and traffic signals and of drivers when it comes to crossing the then look for a gap in the traffic or he/she may begin to streets. They are more likely than younger pedestrians to have watch for a gap long before stepping up to the curb. In the accidents due to problems in information processing, judg- latter case, the pedestrian can adjust his or her walking speed ment, and physical constraints. Other characteristics of older in which to arrive at the curb at the instant a gap is available pedestrians follow (8): in the traffic. Although the pedestrian would experience the same delay as in the first case, the delay may not be counted · Vision is affected in older people by decreased acuity and in a research study. visual field, loss of contrast sensitivity, and slower horizon- Another difficulty in determining pedestrian delay arises tal eye movement. when pedestrians do not comply with street-crossing guide- · They often have difficulty with balance and postural sta- lines. Pedestrian non-compliance occurs when pedestrians do bility, resulting in slower walking speeds and increased not use a crosswalk to completely cross a street or when they chances for tripping. use a crosswalk incorrectly, such as entering the crosswalk in · Selective attention mechanisms and multi-tasking skills front of an approaching vehicle. Although greater non- become less effective with age, so older people may have compliance increases the difficulty in determining pedestrian difficulty locating task-relevant information in a complex delay, greater pedestrian delay generally increases non- environment. compliance. Most studies state that pedestrians become more · They have difficulty in selecting safe crossing situations in likely to take extra risks at longer delays, i.e., above a delay of continuously changing complex traffic situations, likely around 30 s, pedestrians are more likely to accept shorter gaps because of deficits in perception and cognitive abilities, as in traffic through which to cross (21, 22). well as ineffectual visual scanning, limitations in time shar- The Highway Capacity Manual (HCM) (23) includes aver- ing, and inability to ignore irrelevant stimuli. age delay to pedestrians at unsignalized intersections as the · They have difficulty in assessing the speed of approach- measure of level of service (LOS) (see Table 8). The table was ing vehicles, thus misjudging when it is safe to cross the developed with anecdotal evidence that suggests delay to road. pedestrians at unsignalized intersections should be consid- · They have slower reaction time and decision making. ered congruent to delay to vehicles on the cross street at · Those with arthritis may have restricted head and neck unsignalized intersections. The HCM LOS table for vehicles mobility as well as difficulty walking. at two-way stop control is provided as Table 9. The HCM also · There is reduced agility for those who use canes or crutches provides a series of equations to calculate the average delay for assistance. per pedestrian at an unsignalized intersection. The calculated Table 8. HCM LOS criteria for pedestrians at unsignalized intersections. (23) Level of Service Average Delay/Pedestrian (s) Likelihood of Risk-Taking Behavior* A <5 Low B 5 10 C > 10 20 Moderate D > 20 30 E > 30 45 High F > 45 Very High * Likelihood of acceptance of short gaps.
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15 Table 9. HCM LOS criteria for two-way stop control (HCM Exhibit 17-2). (23) Level of Service Average Control Delay (s/veh) A 0-10 B > 10-15 C > 15-25 D > 25-35 E > 35-50 F > 50 value is to be used in conjunction with Table 8 to determine then cross the other side of the street. Finally, if a pedestrian the level of service of the intersection. does not initially see an acceptable gap in the traffic, he or she Complicating matters is the belief that non-compliant may walk down the side of the street while constantly looking pedestrians use several tactics when crossing streets. A 1998 for an acceptable gap through which to cross. This tactic is FHWA report (24) cites a study by Song, Dunn, and Black known as the walk'n-look and is perhaps the most efficient, where all street-crossing tactics were consolidated into four greatly reducing or removing the delay to the pedestrian groups: double-gap, risk-taking, two-stage, and walk'n-look. wishing to cross the street. However, it is not useful when the Double-gappers look for an acceptable gap in the near lane as pedestrian's main travel objective is perpendicular to the well as a gap twice as long in the far lane through which to street. cross in one continuous action. Slower or more cautious Pedestrian delay increases as vehicular traffic volumes pedestrians often use this tactic. A pedestrian is said to increase. As pedestrian volumes increase, however, a prece- employ the risk-taking tactic when he or she accepts the same dent is established whereby motorists begin to expect pedes- size gap in each lane. Two-stage crossings involve pedestrians trians. At these locations, drivers are more likely to yield to who cross one side of the street, take refuge in a median, and pedestrians, which in turn decreases pedestrian delay (25).