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48 Golden single-lane roundabout, the pretest was completed in time was generally rewarded by an all-quiet period that made July 2008 with a total of 18 blind travelers (GOL-PRE). Thirteen crossing very comfortable. of the original 18 participants returned for the posttest study This type of behavior may further explain why the observed in September 2008 (GOL-POST). Again, no treatments were delay was relatively high at an average of 25.3 s. The delay over installed at this roundabout, so the underlying hypothesis is minimum was also high, at 18.0, due the aforementioned inef- that overall performance in pretest and posttest conditions is ficiency in utilizing crossing opportunities. The 85th percentile the same. The Raleigh site was originally studied in a separate delay was expectedly even higher at 35.4 s. Further, these delay research project (NIH 2010) in 2004, with video recordings re- figures mask the fact that some pedestrians experienced even analyzed as part of this project using the NCHRP Project 3-78A higher delays. The maximum average delay experienced by a analysis framework (PS-RAL). The analysis included a total single pedestrian was 74.0 s over 12 trials. The maximum of 12 blind study participants. average delay over minimum was 59.4 s. Appendix A gives additional results for these locations, The site further exhibited an overall low rate of O&M inter- including a discussion of between-participant variability. ventions. In fact only two interventions were observed over the 120 crossings at the entry and exit leg, corresponding to the stated rate of 0.8%. The two interventions (one at entry Crossing Performance Results and one at exit) were recorded for two different participants. Charlotte, NC, Single-Lane Roundabout The remaining participants therefore did not experience any interventions at this site. The field evaluation at the Charlotte single-lane roundabout This analysis points to mixed results in terms of the ques- location (DAV-CLT) yielded mixed results. On the one hand, tion of roundabout accessibility. Clearly, a low intervention participants experienced very little risk in terms of O&M inter- rate speaks to a safe crossing. However, the elevated levels of vention rates; on the other hand, delays experienced by the delay are indicative of significant inconvenience for pedestrians participants were high. Table 4 summarizes the crossing per- who are blind and further may lead people to avoid this cross- formance for the DAV-CLT site. The figures were obtained by ing location. A further cause for concern is that traffic volumes averaging the mean crossing performance of each of the study may increase and reduce the availability of crossable gaps while participants at this location. presumably increasing the level of ambient noise. It is unclear Table 4 shows a very low occurrence of yield opportunities whether yielding behavior would be affected with higher at only 6.3%. The rate of encountering crossable gaps was volumes or would stay the same. As discussed, no treatments higher, at 28.8%, which is explained by generally low traffic were tested at this location, but at higher volumes, a treatment volumes at the site except for some peak-hour traffic surges. intended to increase driver awareness and propensity to yield The rate of utilization of both yields and crossable gaps was may be appropriate. about two thirds of all encounters, suggesting that despite low volumes and associated low levels of ambient noise, partic- ipants had some difficulties at this location. From the rate Raleigh, NC, Single-Lane Roundabout of utilization it is unclear whether these opportunities were The field evaluation at the Raleigh single-lane roundabout missed (i.e., the pedestrian failed to detect them) or rejected. In location (PS-RAL) was intended to test the hypothesis that the fact, several participants indicated that they were aware of the findings at the DAV-CLT site were biased by low conflicting presence of, for example, a yielding vehicle, but nonetheless traffic volumes. The PS-RAL exhibits higher traffic volumes chose to wait. At low conflicting volumes, the additional wait and is further located in a campus environment with more frequent pedestrian activity. It was hypothesized that driver expectations of encountering pedestrians would be elevated, Table 4. Crossing performance summary which would result in an increased propensity to yield. Table 5 at DAV-CLT. summarizes the crossing performance for the PS-RAL site. Performance Measure Mean Std. Dev. The figures were obtained by averaging the mean crossing Yield Opportunities 6.3% 4.9% performance of each of the study participants at this location. CG Opportunities 28.8% 6.8% Table 5 in fact shows a relatively high occurrence of yield Yield Utilization 67.4% 42.3% opportunities at 33.0%. The rate of encountering crossable gaps CG Utilization 63.3% 19.3% was lower than at DAV-CLT, at 19.1%. Combined, over half of Average Delay (s) 25.3 13.8 all vehicle encounters corresponded to crossing opportunities. Delay>Min (s) 18.0 12.8 At higher traffic volumes, this results in relatively frequent 85th Percentile Delay (s) 35.4 crossing opportunities over time. The rate of utilization of yields O&M Interventions 0.8% 2.6% was very high at this site, at 85.4%. This may be explained by

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49 Table 5. Crossing performance summary ity of yields and good utilization of crossing opportunities, the at PS-RAL. observed delays at PS-RAL were relatively low and further do not seem too different from what a sighted pedestrian might Performance Measure Mean Std. Dev. have experienced (see Delay>Min). However, the crossing Yield Opportunities 33.0% 16.6% decisions were characterized by a high intervention rate, which CG Opportunities 19.1% 9.2% raises concerns for pedestrian safety. Since this study was per- Yield Utilization 85.4% 17.3% formed as part of a different research project, no treatments CG Utilization 57.8% 34.4% Average Delay (s) 11.1 7.8 were tested. Delay>Min (s) 5.8 6.4 85th Percentile Delay (s) 19.6 Golden, CO, Single-Lane Roundabout O&M Interventions 3.9% 5.8% The Golden single-lane roundabout was studied concur- rently with a nearby two-lane roundabout. Two rounds of field testing were performed at the same time as the single-lane slower speeds that result in an overall reduced level of ambient roundabout pretest and posttest treatment conditions. Even noise. The rate of crossable gap utilization was just below 60%, though no treatments were installed at the two-lane round- which is in the same region observed at the DAV-CLT site. about, the two test phases are referred to as GOL-PRE and A combination of frequent crossing opportunities and GOL-POST, respectively. Table 6 summarizes the crossing per- high utilization rates expectedly results in relatively low delay formance for the site. The figures were obtained by averaging estimates. The average delay was 11.1 s, and the delay over the mean crossing performance of each of the study partici- minimum was only 5.8 s. The 85th percentile delay was some- pants at this location. what higher at 19.6 s. As with other sites, individual participants Table 6 shows no significant differences in the operational experienced higher average delays, with the maximum average and safety performance during the pretest and posttest condi- observed delay at 34.2 s (24.7 s delay over minimum). tions. It can therefore be concluded that no measurable partic- However, the site exhibited a higher rate of O&M interven- ipant learning effect took place between the two studies and tions, at 3.9%. This rate corresponds to a total of 15 interven- further that driver behavior and traffic patterns were similar. tions, 11 of which were observed at the exit portion of the Both conditions showed a high occurrence of yield opportuni- crossing. The interventions were further distributed across nine ties (over 40% of vehicle encounters) along with some cross- of the 12 participants, suggesting that some risk was evident able gap opportunities (over 20%). The utilization rates for for most of the participants. One participant experienced five both yields and crossable gaps were high, at or above 80%. As interventions across 32 crossing attempts, equivalent to a rate a result, the average delay experienced by participants was of 15.6%. In interpretation of these intervention statistics, it low (around 12 s), and only a very small portion of that delay is important to highlight that a different O&M specialist accom- was due to missed opportunities (delay over minimum was panied the participants in this prior study. Therefore, while about 3 s). The variability in delay was higher at this site, and the the experimental protocol was generally the same, it is possible highest average delay experienced by a participant was 51.4 s. that individual differences of the O&M specialist contributed The intervention rate shows an apparent drop from 1.4% to the difference in interventions. to 0.5% between pretest and posttest conditions, but this The analysis shows the opposite trend of the previously slight difference is not significant. Overall, five interventions studied DAV-CLT site. Due to the relatively frequent availabil- were recorded, four of which occurred in the pretest condition. Table 6. Crossing performance summary at GOL-PRE and GOL-POST. Performance Measure Pre Post Difference p-value Yield Opportunities 40.4% 43.8% 3.4% 0.6398 CG Opportunities 23.5% 21.3% 2.2% 0.5800 Yield Utilization 79.4% 84.7% 5.3% 0.4897 CG Utilization 85.1% 81.2% 3.9% 0.6368 Average Delay (s) 11.9 12.1 0.2 0.9544 Delay>Min (s) 2.8 3.1 0.3 0.8156 85th percentile Delay (s) 22.2 21.7 0.5 O&M Interventions 1.4% 0.5% 0.9% 0.2651