Cover Image

Not for Sale

View/Hide Left Panel
Click for next page ( 46

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 45
45 Table 2. Crossing performance summary, pretest and posttest, at SS+FB CTL. Performance Measure Pre Post Difference p-value Yield Opportunities 15.20% 22.00% 6.80% 0.0363 CG Opportunities 44.70% 49.20% 4.50% 0.444 Yield Utilization 53.10% 64.60% 11.50% 0.2769 CG Utilization 63.20% 89.30% 26.10% 0.0011 Average Delay (s) 23.4 12.2 11.2 0.0453 Delay>Min (s) 14.9 4.9 10.0 0.0342 85th Percentile Delay (s) 38.6 17.9 20.7 O&M Interventions 5.6% 1.40% 4.2% 0.0112 In a synthesis of results from 17 sites, the authors recorded the crosswalk, while the SS-ONLY crossing resulted in seven an observed range in the average yielding rates of from 13% of these events. Given that the two locations had similar traffic to 91%, which suggests that other contributory factors (speeds, volumes and that the starting order for participants was ran- driver population, regional differences) affect yielding behavior. domized, a likely contributory explanation for the difference in Consistent with the research hypotheses, the treatment did intervention rates is related to sound patterns at the crossing. not have a significant impact on the availability of crossable Appendix A gives additional results for the CTL crossings gaps. The rates of utilization for yield and crossable gap oppor- and treatments, including a discussion of inter-participant tunities both saw a significant increase of 11.5% and 26.2%, variability. respectively. Only the CG utilization is statistically significant, but both trends are surprising in light of the fact that the Participant Feedback SS-ONLY treatment did not show the same results. A possible explanation is proposed: It is hypothesized that the auditory Following each of the pretest and posttest studies, partici- message that accompanied the flashing of the beacon gave pants were asked a series of questions about their perceptions pedestrians additional confidence. The primary intent of the of the crossing and their level of confidence in their crossing treatment was to alert the approaching driver to the pedestrian's decisions. The blank survey forms are provided in Appendix G. crossing intent and increase yielding. However, the audible While participants seemed somewhat more confident during message provided an auditory confirmation to the pedestrian the treatment conditions, their feedback generally indicated that the beacon was flashing and appears to have contributed some uncertainty in crossing at the CTL locations. However, in some way to the willingness of pedestrians to utilize cross- this level of uncertainty didn't seem to quite reach the level that ing opportunities. However, it's not clear that the pedestrians may be expected from the high delay and intervention rates at were able to confirm the opportunity auditorily. The O&M this site. The average of the responses on the confidence ques- specialist who was monitoring participants was concerned tion ("How would you rate your confidence in your ability to that the auditory message masked some vehicular sounds and cross here safely on a scale of 1 to 5, with 1 being not at all and could encourage crossings that were more risky because some 5 very confident?") was 3.66 in the pretest, and 4.0 and 4.1 in participants seemed to rely more on the vehicles yielding, with- the SS-ONLY and SS+FB posttests, respectively. out confirmation, when the flasher was present. These numbers seem to indicate a false sense of participant In the tested combination, the SS+FB treatments had a confidence in their ability, if measured by the rate of interven- large effect on the pedestrian delay as well as a reduction in tions. One participant who rated her confidence in crossing O&M interventions. Average delay and the delay over mini- safely at 4 said: "but maybe it's too dangerous. I knew you were mum were both reduced significantly, by 1011 s, and the behind me to grab me." Another said: "It's a little risky; I could 85th percentile delay was reduced by over 20 s. O&M inter- make mistakes." Although the team instructed participants to ventions were reduced significantly, from 5.6% to 1.4%, which cross only if they would do so if they were alone, without an reduced the likelihood of a potentially dangerous event from O&M specialist, it seemed that they felt they should try to one in 18 decisions to one in 71. The raw count of interven- cross to help us in our research. Participants repeatedly were tions was 14 in the pretest and four in the posttest conditions, reminded that even the fact that they reached the 2-min time- and both counts are lower than at the SS-ONLY crossing. It out or decided not to cross were valuable research findings. is unclear what the specific reason for this difference in inter- However, all participants attempted to cross and very few peo- ventions is between the two crossing locations. Of the 14 pretest ple actually timed out. It is possible that the 2-min time limit interventions, only one was associated with a stopped car on was longer than participants were willing to wait.