Evaluation of Safety Strategies at Signalized Intersections (2011) / Chapter Skim
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Chapter 2 - Literature Review
Chapter 2 - Literature Review
Pages 7-12
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From page 7... ...
This qualitative measure reflects the level of predictive certainty in the CMF derived and is a reflection of the study methodology. The confidence levels and the levels of predictive certainty can be qualified as follows: • High -- The CMF was developed in a rigorous observational before-after study that incorporates what are currently considered the best study design and statistical analysis methods, namely the empirical Bayes (EB)
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From page 8... ...
to try to deduce the effect on safety. • Rakha et al., 2000 • Berg et al., 1986 seidutsyekoNtnetsixE-noNPnoitpmeerpelcihevycnegremeyolpmE:5A2.71 17.2 A6: Improve operation of pedestrian and bicycle facilities at signalized intersections: • Pedestrian signs, signals, and markings • Crossing guards for school children • Lights in crosswalks in school zones • Pedestrian-only phase or pedestrian-lead phase during signal operation Combination of P and T Low for Pedestrian Signals • Zegeer et al., 1982 • Elvik and Vaa, 2004 17.2 A6: Improve operation of pedestrian and bicycle facilities at signalized intersections: Prohibition of RTOR Combination of P and T Low-Medium • Preusser et al., 1982.
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From page 9... ...
• NCHRP Project 3-89 (ongoing) Psenalnrut-thgirnehtgneL:2B2.71 Non-Existent No Key Studies 17.2 B3: Improve geometry of pedestrian and bicycle facilities: • Continuous sidewalks • Signed and marked crosswalks • Sidewalk set-backs • Median refuge areas • Pedestrian overpasses • Intersection lighting • Physical barriers to restrict pedestrian crossing maneuvers • Relocation of transit stops • Other traffic calming applications Combination of P and T Non-Existent The following studies the safety effects of marked versus unmarked crosswalks at unsignalized locations.
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From page 10... ...
• Elvik and Vaa, 2004. 17.2 B4: Revise geometry of complex intersections – convert two T intersections to one four-leg intersection T Non-Existent No key studies 17.2 B4: Revise geometry of complex intersections – improve intersection skew angle P Non-Existent No key studies 17.2 B4: Revise geometry of complex intersections – Remove deflection in through-vehicle travel path T Non-Existent No key studies 17.2 B4: Revise geometry of complex intersections – Close intersection leg T Non-Existent No key studies 17.2 B5: Construct special solutions: provide indirect left turn T Non-Existent No key studies 17.2 B5: Construct special solutions: Convert to roundabout T Medium High • Persaud et al., 2001.
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From page 11... ...
17.2 D2: Improve visibility of signals and signs at intersections: • Provide visors to shade signal heads • Provide louvers, visors, or special lenses so drivers are able to view signals only for their approach • Install backplates T Medium High for Signal Lens Upgrade The following study conducted a before-after EB evaluation using a combination of different treatments to improve visibility. Different groups of intersections had a slightly different set of treatments.
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From page 12... ...
; From NCHRP Report 500, Volume 12. Table 2.1.
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