1. Role of Safety Performance Functions in the Highway Safety Manual July 29, 2009

2. Presentation Overview SPF Application in Part C: Predictive Method SPF Application in Part B: Roadway Safety Management Process

3. Safety Performance Functions in Part C – Predictive Method

4. SPFs in Part C – Predictive Method

5. SPF for specific facility type AADT Length Site characteristics to adjust with AMFs – Roadway – Intersection Local Calibration Factor Crash data for EB Method application Summary Data Needs for SPF Application

6. Application of SPFs in Part C  1.5-mi rural two-lane  Tangent roadway segment  10,000 veh/day  0% grade  Local calibration factor = 1.10  6 driveways per mi  10-ft lane width  4-ft gravel shoulder  Roadside hazard rating = 4  N observed = 10 crashes/year Objective: -Calculate predicted average crash frequency (N predicted )

7. Step 1 - Base Conditions Estimate (N spf ) Predictive Method Sample Application Crashes/year Step 2 – Estimate Predicted Average Crash Frequency

8. Safety Performance Functions in Part B – Roadway Safety Management

9. SPFs and Part B – Roadway Safety Management

10. Chapter 4 – Network Screening

12. Excess Predicted Average Crash Frequency Using SPFs

13. Estimate Crash Reduction on Suburban Arterial Intersection Chapter 7 – Economic Appraisal

14. Estimate Crash Reduction Predicted Crashes - INTERSECTION – Predict Future Crash Frequency with SPF Data needs: SPFs, Future AADT, Length – Apply AMFs and Calibration Factor to Account for Local Conditions Data needs: AMFs for existing condition, local calibration factor Predicted Crashes - ROUNDABOUT – Apply AMF to Account for Alternate Conditions (Roundabout) Data needs: AMFs for alternate condition

15. Estimate Monetary Benefit Convert crash difference to monetary benefits and estimate annual savings of improvement Crash Severity Comprehensive Crash Costs Fatality (K)$4,008,900 Disabling Injury (A)$216,000 Evident Injury (B)$79,000 Fatal/Injury (K/A/B)$158,200 Possible Injury (C)$44,900 PDO (O)$7,400 Source: Crash Cost Estimates by Maximum Police-Reported Injury Severity within Selected Crash Geometries, FHWA - HRT - 05-051, October 2005.

16. Summary of Data Needs for SPF Application Applicable SPF AADT Length Local Geometric/Operational Conditions and Corresponding AMFs Local Calibration Factors Historical crash data for EB Method Application

17. Thank you! www.highwaysafetymanual.org

18. SPFs in Part C – Predictive Method Expected Average Crash Frequency from EB Approach Predicted Average Crash Frequency from SPF Equation Observed Crash Counts

19. Crashes/year Predictive Method Sample Application Step 3 – Estimate Expected Average Crash Frequency

20. Chapter 9 - Safety Effectiveness Evaluation