Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges (2021) / Chapter Skim
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Pages 93-116
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From page 93... ...
5-1 This chapter presents generalized design treatments that may apply to any intersection, including A.I.I.s. Although examples of generic intersections or specific A.I.I.s may be used, the concepts in this chapter are intended to apply to a broader set of intersection configurations.
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From page 94... ...
5-2 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges A.I.I., rather than degraded to a lower-class alternative. For example, a facility with a separate shared-use path along a roadway should not be terminated with an on-street, shared-lane facility or striped bike lane through the A.I.I.
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From page 95... ...
Generalized Design Treatments 5-3 recognizes that pedestrians and bicyclists will not travel at the edge of a facility or immediately against a wall, abutment, barrier, or other structural elements. Vertical structural elements may also affect sight distance.
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From page 96... ...
5-4 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges • Deflection: Horizontal deflection, which can be introduced with a median treatment, controls the fastest speeds at which drivers can comfortably approach the intersection, thereby reducing speeds. Speed may be controlled at the key curves through an A.I.I., most of which include several conflict points.
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From page 97... ...
Generalized Design Treatments 5-5 Depending on the configuration of the A.I.I., large channelization islands may be present. Pedestrians need clear guidance and information on where they should walk and where they should cross.
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From page 98... ...
5-6 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges should be used to define the boundaries of the pedestrian walkway and give pedestrians routing cues in very large channelization islands (see Exhibit 5-5)
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From page 99... ...
Generalized Design Treatments 5-7 • Provide accessible pedestrian signals with pushbutton locator tone at signalized crossings. • Locate pushbuttons to be accessible by wheelchair users and adjacent to the crossing at a minimum separation of 10 feet.
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From page 100... ...
5-8 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges The choice of crosswalk design depends on the context. As a starting point, designers should begin with perpendicular crosswalks at uncontrolled crossings and parallel crosswalks at controlled crossings.
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From page 101... ...
Generalized Design Treatments 5-9 • If decision points are not properly segregated for the motorist (pedestrian yielding versus merging into the travel lane) , the motorist may be looking for gaps in traffic and fail to yield to crossing pedestrians.
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From page 102... ...
5-10 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges • Pedestrian hybrid beacons (PHBs) with accessible pedestrian signals, • Raised crosswalks, and • Fully signalized crossings that are coordinated with the main intersection and with accessible pedestrian signals.
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From page 103... ...
Generalized Design Treatments 5-11 • Providing adequate corner sight distance at the intersection from the stop bar to separate the two areas in space; and • Considering queue storage for a motorist to wait between the crossing and conflicting traffic flow when wanting to turn right on red (providing separation between driver decisions)
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From page 104... ...
5-12 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges This design feature is not exclusive to A.I.I.s; it is a feature of any intersection with left-turn lanes. This left-turn option minimizes out-of-direct travel but may come at the expense of sustained exposure, conflict points, and stressful riding conditions.
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From page 105... ...
Generalized Design Treatments 5-13 could require significant geometric changes to the initial roadway design to provide adequate sight distance and encourage the desired yielding behavior. Some A.I.I.s may also require careful coordination of signals for pedestrians and bicyclists.
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From page 106... ...
5-14 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges • Multistage Crossing: In these cases, the crossing is broken into one or more components, and each crossing is controlled separately. The phases for each crossing generally occur within the same signal cycle, although phases may span the end of the first cycle and beginning of the next cycle.
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From page 107... ...
Generalized Design Treatments 5-15 motorist's view of the vulnerable user is not only obstructed by the first vehicle (Exhibit 5-13) , but the vulnerable user's view of the approaching second vehicle is also blocked by the first vehicle (Exhibit 5-14)
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From page 108... ...
5-16 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Multiple-threat conditions may also exist at signalized locations when permissive turns or right-turn-on-red are allowed by multiple left- or right-turn lanes. Where these turns are permitted across crosswalks showing pedestrian Walk indications, visibility of pedestrians can be reduced along with the ability to yield without affecting through traffic.
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From page 109... ...
Generalized Design Treatments 5-17 5.3.5 Pavement Markings Pavement markings are key to communicating right-of-way between users and alerting motorists and nonmotorists to the possible presence of other intersection users. High-visibility crosswalk markings have been shown to increase motorist yield rates and yielding distance and increase pedestrian scanning for vehicle conflicts before crossing (10)
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From page 110... ...
5-18 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges should provide adequate pedestrian clearance time to ensure that pedestrians are not within the crossing when conflicting traffic movements are released. Pedestrian signals with countdown displays are recommended for conveying remaining phase time to crosswalk users in compliance with MUTCD requirements (9)
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From page 111... ...
Generalized Design Treatments 5-19 There is no universally optimal solution for providing pedestrian crossings along the dimensions of operations, delay, and safety. However, the tradeoffs presented here should allow the designer to consider the design option that matches the desired performance outcome.
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From page 112... ...
5-20 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 5.4.2 Uncomfortable/Tight Walking Environment Design techniques and treatments can include • Widening the sidewalk. • Illuminating the walking environment.
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From page 113... ...
Generalized Design Treatments 5-21 5.4.8 Long Red Times Design techniques and treatments can include • Reducing the overall cycle length. • Modifying the phase sequence to reduce the total crossing time.
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5-22 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 5.4.14 Riding in Mixed Traffic Design technique and treatments can include • Separating bicyclists from motor vehicles through dedicated protected lanes. • Designing for lower motor vehicle speeds where bicyclists and motorists interact.
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From page 115... ...
Generalized Design Treatments 5-23 • Installing a signal to control the channelized movement. • Designing channelization to manage vehicular speeds through the use of compound curves.
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