Guidelines for the Application of Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities (2016) / Chapter Skim
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NCHRP 3-78b: Final Project Report April 2016 5 2 LITERATURE REVIEW It has been well documented in past research that pedestrians who are blind can face significant accessibility challenges when crossing at modern roundabouts or intersections with channelized right turn lanes. As a result of a systematic and iterative research program, researchers (many of whom are on this team)
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NCHRP 3-78b: Final Project Report April 2016 6 Arguably, the fourth component, the safety criterion, is the most important aspect to ensure a safe and accessible crossing environment, while the delay criterion is a term typically used in traffic engineering assessments of (sighted) pedestrian Levels of Service.
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NCHRP 3-78b: Final Project Report April 2016 7 Figure 2-1: Blind pedestrian crossing at multi-lane roundabout This figure shows two pedestrians crossing at a multilane roundabout, one with a white cane extended. Vehicles are yielding in each lane.
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NCHRP 3-78b: Final Project Report April 2016 8 "In trials on the straight roadway, as the ambient sound level increased, the detection times decreased. Once the ambient sound level is above approximately 50 dBA, it becomes virtually impossible to hear vehicles far enough away to know whether it is clear enough to be able to complete a crossing before the vehicles arrive." At CTLs and roundabouts, the ambient sound levels will often be above 50dBA so the safety of crossing in detected gaps in traffic at most roundabouts and CTLs is questionable.
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NCHRP 3-78b: Final Project Report April 2016 9 vehicles in the lane to be crossed. The same is true at CTLs, where the movement of vehicles in other lanes can mask the sound of closer traffic in the channelized lane, negating somewhat the safety benefits of a separated single-lane crossing for individuals who are blind.
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NCHRP 3-78b: Final Project Report April 2016 10 intended to be detected by a person approaching at an angle (ISO 23599)
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NCHRP 3-78b: Final Project Report April 2016 11 2.4 Overview of Research on Treatments to Reduce Crossing Risk for Blind Pedestrians In order to inform the site selection and treatment evaluation, a summary of existing and prior research on treatment effectiveness on roundabout and channelized turn lane accessibility is provided below. 2.4.1 A Synthesis of Crossing Treatment Effectiveness From the completed NCHRP 674 report, two treatments emerged that showed particular promise: the Pedestrian Hybrid Beacon (PHB, also known as a HAWK signal or HAWK beacon)
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NCHRP 3-78b: Final Project Report April 2016 12 This exhibit shows pictures of four existing treatments including: (a) an overhead flashing beacon at a single-lane roundabout approach in Lacey, WA, (b)
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NCHRP 3-78b: Final Project Report April 2016 13 Table 2-2: Summary of Results RRFB. (RCOC 2011, FHWA TOPR34 Study)
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14 NCHRP 3-78b: Final Project Report April 2016 Table 2-3: Summary of Results for Other Treatments. (Schroeder et al., 2011a and RCOC 2011)
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15 NCHRP 3-78b: Final Project Report April 2016 accessibility through geometric treatments and modifications to the site in question. In particular, geometric treatments that encourage (a)
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16 NCHRP 3-78b: Final Project Report April 2016 The authors further tested varying pedestrian and vehicle volumes, as well as single-lane and multi- lane roundabouts. For this discussion, only some of the two-lane roundabout results are presented.
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17 NCHRP 3-78b: Final Project Report April 2016 installation, 12.6% of drivers observed during the solid red did not stop at the PHB (RCOC, 2011)
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18 NCHRP 3-78b: Final Project Report April 2016 -- - This page intentionally left blank -- -
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