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                        Applying Safety Data and Analysis to Performance – Based Transportation Planning


            
            In This Section
        Zero Deaths and Safe System
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                Appendix B. Safety Analysis Objectives and Methods
Table B.1 Safety Analysis Categories, Questions, Tools, and Data Needs
	Analysis Category
			Safety Analysis Question
			What tools are available?
			Data NeedsBenchmarking
			How many fatalities and serious injuries are occurring in my area?
				How does this compare to other areas or my State?
			Descriptive Statistics
				FARS data
			Total crashes
				Total fatalities and serious injuries
				High-level roadway data—roadway ownership, functional classification
				Agency geographic boundary informationIdentify Crash Trends and Contributing Factors
			Who is involved in crashes?
				When are the crashes occurring?
				What are the major contributing factors to crashes?
			Descriptive Statistics
				Trend analysis
			Crash severity—fatality, injury type, property damage, only
				Crash incidence data—time of day, day, month, weather, etc.
				Crash type—road departure, intersection, head-on, angle, etc.
				Contributing factors—age, impairment, seatbelt usage, speed, etc.Identify and Evaluate Focus Crash Types
			What are the most common crash types?
				What are the most common contributing factors?
				What are the characteristics of the overrepresentation?
			Descriptive Statistics
				GIS Mapping
				Scatterplot
				Overrepresentation
				Risk Ratio
			Crash severity—fatality, injury type, property damage, only
				Crash incidence data—time of day, day, month, weather, etc.
				Crash type—road departure, intersection, head-on, angle, etc.
				Contributing factors—age, impairment, seatbelt usage, speed, etc.Network Screening—Identify Sites for Safety Improvement
			What locations (intersections or segments) show the most potential for safety improvements?
			AASHTO HSM Part B Network Screening—Includes descriptive and predictive methods
				AASHTOWare Safety AnalystTM
				GIS Heat Mapping
			Crash severity
				Crash location
				Roadway and roadside characteristics—intersection control, number of lanes, presence and type of shoulder, presence and type of median, posted speed, horizontal and vertical alignment, etc.
				Traffic volume data—intersection total entering traffic volume, roadway segment volume per million vehicle miles
				Calibrated safety performance functions, if predictive methods are usedSystemic Analysis—Identify Safety Risk Factors
			What are the common characteristics of locations with crashes?
				What are the countermeasures to address these characteristics?
				How should we prioritize systemwide implementation?
			FHWA Systemic Safety Project Selection Tool
			Crash severity
				Crash location
				Roadway and roadside characteristics—intersection control, number of lanes, presence and type of shoulder, presence and type of median, posted speed, horizontal and vertical alignment, etc.
				Traffic volume data—intersection total entering traffic volume, roadway segment volume per million vehicle milesCorridor and Intersection Planning Safety Analysis
			What are the safety effects of alternative roadway or intersection cross sections?
			AASHTO HSM Part C Predictive Method and NCHRP 17-38 Spreadsheets
				Interactive Highway Safety Design Model (IHSDM)
				Crash Modification Factors (e.g., FHWA Crash Modification Factor Clearinghouse)
				Collision Diagrams
			Crash severity
				Crash location
				Roadway and roadside characteristics—intersection control, number of lanes, presence and type of shoulder, presence and type of median, posted speed, horizontal and vertical alignment, etc.
				Traffic volume data—intersection total entering traffic volume, roadway segment volume per million vehicle miles
				Calibrated safety performance functions if predictive methods are used
      
  Book traversal links for Appendix B. Safety Analysis Objectives and Methods
      ‹ 7.0 Conclusions
                    Up
                    Appendix C. Risk Ratio ›
                
                Book:Applying Safety Data and Analysis to Performance – Based Transportation Planning
              1.0 Introduction
                2.0 Audience, Purpose, and Guidebook Structure
                3.0 Performance-Based Planning Processes
                4.0 Getting Started with Transportation Safety Planning—Data Collection
                5.0 Using Safety Analyses for Planning
                7.0 Conclusions
                Appendix B. Safety Analysis Objectives and Methods
                Appendix C. Risk Ratio
                Appendix D. Regression to the Mean U.S. DEPARTMENT OF TRANSPORTATION

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