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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).
