Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities (2011) / Chapter Skim
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Pages 34-42
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From page 34... ...
: the probability of encountering a yield in the traffic stream. The definitions for what constitutes a yield or a crossable gap are given later in this chapter.
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From page 35... ...
The utilization of crossable gaps is a function of the gap acceptance characteristics of the pedestrian. It may further be influenced by background noise at the site.
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From page 36... ...
Another caveat of the utilization measure is that it can be used to describe potentially risky behavior. For example, assuming that the defined threshold for a crossable gap is appropriate, any utilization of a non-crossable gap has the potential of increasing the rate of crossable gap utilization to something greater than 100%.
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From page 37... ...
Similarly, the probability of utilizing a crossable gap is expected to be high, given that the threshold for what is considered crossable is high for 85% of the general pedestrian population. Nonetheless, the chosen walking speed is considered a reasonable assumption in light of national policy documents like the MUTCD, and in light of the fact that the threshold is consistently applied to all sites to allow for a relative comparison.
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From page 38... ...
Gap Events (n=6) CG This figure shows an illustrative example of how pedestrian–vehicle events are determined in the NCHRP Project 3-78A analysis framework.
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From page 39... ...
• Yield Lost Time (s) : The yield lost time (YLT)
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From page 40... ...
Definitions of the utilization measures are consistent with the single-lane analysis framework. For the purpose of this analysis, it is assumed that only events with a crossing opportunity (either a yield or crossable gap)
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From page 41... ...
The figure shows three possible event states for the lane nearest to the pedestrian: yield, crossable gap, and non-crossable gap. Each of these three event states can be associated with the same three event outcomes in the far lane for a total of nine event combinations.
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From page 42... ...
and P(GO|Y) , • Sound strips: Increase P(GO|Y)
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