MassDOT Safety Alternatives Analysis Guide PREPARED FOR July 2020 MassDOT Safety Alternatives Analysis Guide Table of Contents Executive Summary .....................................................................................................................................................................................2 Introduction ...................................................................................................................................................................................................4 Defining Safety ..............................................................................................................................................................................................4 Safety Performance Functions ...........................................................................................................................................................5 Crash Modification Factors .................................................................................................................................................................5 Empirical Bayes (EB) ...............................................................................................................................................................................6 Data ...................................................................................................................................................................................................................7 Crash Data ........................................................................................................................................................................................7 Traffic Volume Data........................................................................... ...........................................................................................7 Roadway Data .................................................................................................................................................................................8 Alternatives Analysis ...................................................................................................................................................................................9 Step 1 – Future No-Build Safety Performance .......................................................................................................................... 11 Method 1 – Expected Crash Frequency via Empirical Bayes .......................................................................................... 11 Method 2 – Predicted Crash Frequency................................................................................................................................. 14 Method 3 – Observed Crash Frequency ................................................................................................................................ 15 Step 2 – Expected Change in Safety Performance .................................................................................................................. 17 Application of Multiple CMFs .................................................................................................................................................... 17 Step 3 – Economic Analysis ..............................................................................................................................................................20 Step 3A: Determine Average Crash Cost for Study Site’s Facility Type ...................................................................... 22 Step 3B: Convert Crash Reductions to Annual Savings .................................................................................................... 23 Step 3C: Calculate Lifetime Benefits ........................................................................................................................................ 24 Step 3D: Calculating Benefit-Cost Ratio ................................................................................................................................ 24 Interpretation of Results .........................................................................................................................................................................24 Documentation ..........................................................................................................................................................................................24 Useful Tools .................................................................................................................................................................................................25 Massachusetts Intersection Crash Prediction Tool.................................................................................................................. 25 MassDOT Intersection Control Evaluation ................................................................................................................................. 27 Example.........................................................................................................................................................................................................27 Step 1 – Future No-Build Safety Performance with Method 1 ........................................................................................... 28 Step 1 - Future No-Build Safety Performance with Method 2 ........................................................................................... 35 Step 1 - Future No-Build Safety Performance with Method 3 ........................................................................................... 37 Step 2 – Expected Change in Safety Performance .................................................................................................................. 38 Alternative 1- Turn Lanes .............................................................................................................................................................38 Alternative 2 – Signalization .......................................................................................................................................................40 Alternative 3 – Conversion to Roundabout .......................................................................................................................... 42 Step 3 – Economic Analysis ..............................................................................................................................................................43 Interpret Results ...................................................................................................................................................................................45 Conclusions and Recommendations ................................................................................................................................................. 45 ii MassDOT Safety Alternatives Analysis Guide References....................................................................................................................................................................................................46 Appendix A – State-Preferred CMF List ............................................................................................................................................ 47 Appendix B – Relevant Links .................................................................................................................................................................53 Appendix C – Safety Performance Functions ................................................................................................................................. 54 iii MassDOT Safety Alternatives Analysis Guide List of Acronyms A Incapacitated Injury or Suspected Serious Injury AADT Annual Average Daily Traffic B Non-Incapacitating Injury or Suspected Minor Injury C Possible Injury CMF Crash Modification Factor CMFunction Crash Modification Function EB Empirical Bayes FAST Fixing America’s Surface Transportation FHWA Federal Highway Administration FI Fatal and Injury Crashes HSIP Highway Safety Improvement Program HSM Highway Safety Manual ICE Intersection Control Evaluation K Fatal Injury MAP-21 Moving Ahead for Progress in the 21st Century MassDOT Massachusetts Department of Transportation MMUCC Model Minimum Uniform Crash Criteria O No Apparent Injury PDO Property Damage Only SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equality Act: A Legacy for Users SPF Safety Performance Function SPICE Safety Performance for Intersection Control Evaluation VPD Vehicles per Day iv MassDOT Safety Alternatives Analysis Guide List of Tables Table 1 Summary of facility types for which MassDOT has calibrated HSM SPFs for analysis. ...................................5 Table 2 Features required for MassDOT-calibrated urban and suburban intersection HSM SPFs. ...........................8 Table 3 A list of variables used throughout the document. ......................................................................................................10 Table 4 Massachusetts-adjusted comprehensive crash costs in 2019 dollars. ..................................................................21 Table 5 Average comprehensive FI and PDO crash costs by facility type in 2019 dollars. ............................................22 Table 6 Observed crash data for example intersection. 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