Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities (2011) / Chapter Skim
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Pages 99-139
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From page 99... ...
99 This appendix contains five parts detailing analysis results for the different studies performed under NCHRP Project 3-78A: Part 1: Detailed Channelized Turn Lane Results Part 2: Detailed Single-Lane Roundabout: Golden, CO Part 3: Detailed Single-Lane Roundabout: North Carolina Part 4: Detailed Two-Lane Roundabout: Golden, CO – RCW Part 5: Detailed Two-Lane Roundabout: Golden, CO – PHB A P P E N D I X A Detailed Results
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C O N T E N T S 101 Part 1 Detailed Channelized Turn Lane Results 101 Introduction 101 CTL Analysis Results 101 Site Description 101 Crossing Statistics for CTL Site and Treatments 108 Channelized Turn Lane Results Summary 110 Part 2 Detailed Single-Lane Roundabout: Golden, CO 110 Introduction 110 Golden Single-Lane Analysis Results 110 Site Description 110 Crossing Statistics for Crosswalk 115 Golden, CO, Single-Lane Roundabout Summary 116 Part 3 Detailed Single-Lane Roundabout: North Carolina 116 Introduction 116 North Carolina Single-Lane Analysis Results 116 Site Description 118 Crossing Statistics 120 Discussion 121 Part 4 Detailed Two-Lane Roundabout: Golden, CO – RCW 121 Introduction 121 Raised Crosswalk Evaluation 121 Raised Crosswalk Treatment Overview 121 Pretest Pedestrian Behavior at the RCW 123 Posttest Pedestrian Behavior at the RCW 124 Performance Statistics for RCW 127 RCW Summary 128 Part 5 Detailed Two-Lane Roundabout: Golden, CO – PHB 128 Introduction 128 Pedestrian Hybrid Beacon Evaluation 128 Pedestrian Hybrid Beacon Treatment Overview 128 Pretest Pedestrian Behavior at the PHB Crosswalk 130 Posttest Blind Pedestrian Behavior at the PHB Crosswalk 133 Performance Statistics at the PHB Crosswalk 136 Driver Behavior at the PHB 138 PHB Crosswalk Summary 100
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Vehicle movements were entirely uninhibited and free flowing during signal phases where the downstream lanes were clear, which were the signal phases serving the adjacent through movements on Providence Road and the opposing left turns on PinevilleMatthews Road. The treatments tested at the CTL site were intended to provide a relatively low-cost solution to make the site accessible to and usable by pedestrians who are blind.
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Exhibit 4 shows that the probability of encountering a yield, P(Y_ENC) , was not significantly different at the two studied crosswalks in the pre condition (p = 0.2728)
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Exhibit 5 shows the statistics for the studied crosswalk. The results in Exhibit 5 show a slightly higher P(CG_ENC)
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Average pedestrian delay statistics for studied crosswalk.
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Exhibit 8 shows the 85th percentile delay estimate by subject for SS-ONLY (a)
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time slot experienced lower delay than those participating later in the day, when traffic volumes were higher. However, given the low sample of observations in each category, no effect can be isolated.
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• Yield Lost Time (s) : The YLT is defined as the time between when a driver first yields and the time the crossing is initiated.
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While fewer average interventions were observed at the SS+FB crosswalk compared to SS-ONLY, the difference is not statistically significant (p = 0.1614)
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. SS-ONLY Turn Lane SS+FB Turn Lane Performance Measure Pre Post Pre Post Yield Availability 18.4% 18.6% 15.2% 22.0% Gap Availability 34.9% 41.2% 44.7% 49.2% Yield Utilization 50.8% 40.5% 53.1% 64.6% Gap Utilization 60.3% 68.2% 63.2% 89.3% 85th percentile Delay (s)
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Again, no treatments were installed at this roundabout, so the underlying hypothesis is that overall performance in pre and post conditions are the same. Golden Single-Lane Analysis Results Site Description A picture of the studied crosswalk is shown in Exhibit 14.
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Entry 80.3% 21.3% 100.0% 23.3% Exit 89.2% 66.7% 100.0% 12.7% Overall 84.7% 23.1% 100.0% 18.9% Exhibit 15. Yield availability and utilization statistics for studied crosswalk.
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Exhibit 16. Crossable gap availability and utilization statistics for studied crosswalk.
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Exhibit 19 shows the 85th percentile delay estimate by subject. It appears that one participant (subject 7)
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Entry 2.8 0.1 6.6 2.3 Exit 1.1 –1.4 4.4 1.8 Overall 1.9 –1.4 6.6 2.2 Exhibit 20. Latency and yield lost time statistics for studied crosswalk.
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Exhibit 23 summarizes the crossing performance for the Golden single-lane roundabout. In a comparison to other single-lane roundabouts, the Golden roundabout showed a higher rate of driver yielding and a comparable rate of crossable gap occurrence.
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One of the uses of these funds was the evaluation of the second single-lane roundabout described in this document. The roundabout at the intersection of Pullen Road and Stinson Drive in Raleigh was previously studied in a related project, using the same experimental protocol applied in NCHRP Project 3-78A.
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198 26 272 39 535 PM Peak (5:00-6:00PM) 364 70 277 76 787 DAV-CLT Peak Hour Volumes Total Entering Volumes, Nov-2007 Exhibit 25.
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Yield encounters and utilization statistics for studied crosswalk.
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Exhibit 27 shows the statistics for the studied crosswalks. Exhibit 27a shows the encounters of crossable gaps at the two sites.
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These two factors seemed to have a significant overall impact on reduced pedestrian delay, despite the fact that the site had higher volumes and consequently a lower availability of crossable gaps, P(Gap>Min)
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The analysis defines the vehicle state in the near lane in five event categories: 1. Rolling Yield (RY)
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The corresponding overall rate of yield utilization is 45.4%, but 16.4% of utilized yields in the near lane were forced by the pedestrian seizing the crosswalk. The analysis of the far-lane event shows that a majority of the non-utilized yields were attributable to either non-crossable gaps or multiple events in the far lane.
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The likelihood of encountering 123 Pre (n = 686) Near Lane Far Lane Availability Statistics P(Y_Enc)
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. However, the rate of crossable gap utilization increased from 78.9% to 93.8% in the near lane.
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Exhibit 39 shows the cumulative distribution of pedestrian delay at the PHB. The 85th percentile delay is highlighted.
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5.4 2.2 11.2 2.4 b) Yield Lost Time (s)
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. The effect on the behavioral parameters was large enough to significantly impact the bottom line in the form of greatly reduced delay and the reduction of O&M interventions to zero.
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. The analysis presents findings in the pre and post conditions for the studied crosswalk sequentially.
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The analysis defines the vehicle state in the near lane in five event categories: 1. Rolling Yield (RY)
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In total, pedestrians encountered 28.7% crossable gaps in both the near and far lanes. In the near lane, 87.3% of crossable gaps were utilized, along with 89.0% in the far lane.
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Events in the "Walk" phase include a significant number of rejected events (28.0%) , mostly in the form of non-crossable gaps.
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0 Stopped Yield Utilized 5 Non-Utlz. 0 Forced Yield Utilized 10 Non-Utlz.
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Near Lane Far Lane Availability Statistics P(Y_Enc)
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Exhibit 56 shows the cumulative distribution of pedestrian delay at the PHB. The 85th percentile delay is highlighted.
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-0.4 -5.1 3.3 2.1 Exhibit 58. Latency and yield lost time statistics for PHB crosswalk.
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40 crossings (for example two crossings a day over 4 weeks with 5 working days per week)
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The increases in average maximum queues are significant at p < 0.0001. With available queue storage of two vehicles (one per lane)
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With the installation of the PHB, that proportion of maximum queues greater than two vehicles increased from 29.8% to 69.2%. However, the average queue is expected to be much lower, so that the overall effect of the PHB installation on vehicle queues is considered to be marginal.
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68.9% 95.0% Gap Utilization* 88.2% 100.0% 85th Percentile Delay (s)
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