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APPENDIX A Treatment Implementation Process Framework The framework shown in Exhibit A-1 provides an outline of basic steps needed to evaluate an intersection and consider possible speed reduction treatments. 65
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66 Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections INTERSECTION PRE-SCREENING Determine the need for intersection study Reports of high speeds, high crash frequency and/or severity, recurring crash types, and/or near misses Gather intersection data Environment Speed Data Rural/urban/suburban 85th -percentile speed "Open" or "closed" cross section Mean speed Building offsets Speed variance Landscaping Traffic Visual complexity Volume Pedestrians/bicycles Composition User (commuter, recreational, tourist) Intersection Features Crash Records Control type Type Sight distance Severity Unconventional features Intersection configuration Lane drops/merging Segment/intersection relationship Lighting Weather Other geometric issues Time of day Assess Data Potential Scenarios Reason Speeds Are High Speeds are high, but no crashes occur: Is Willful violation speed reduction needed? Inappropriate posted speed Speeds are high and crashes do occur: Will Environment contributes to speed (speed speed reduction reduce crashes? adaptation, lack of awareness, poor Speeds are appropriate, but crashes occur: visibility) Is additional speed reduction needed? Congestion patterns Issues of High Speed Role of Speed Uniformity of flow Is speed itself an issue? Prevailing speeds above posted Where is speed an issue? Segment, transition, and intersection Exhibit A-1. Treatment implementation process framework.
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Treatment Implementation Process Framework 67 TREATMENT SCREENING Fatal-Flaw Analysis Approach type Control type Physical constraints Cost Noise Maintenance Detailed Treatment Evaluation Target Speed Effects Design Speed effects Posted Safety effects Operating Maintenance Approach Type Potential Secondary Impacts Major or minor Capacity Stop-controlled Pedestrians/bicycles Signalized ADA Uncontrolled Land use Yield-controlled Economics Enforcement needs Type of Treatment Construction Isolated Continuous Combination TREATMENT IMPLEMENTATION Design Geometric and operational influence areas Opportunities to reinforce existing treatments/features Distance required for speed transition Perceptionreaction distance Driver workload Opportunities to combine treatments Implementation Address public education and awareness Consider construction impacts Create evaluation plan Exhibit A-1. (Continued).