FHWA-TS-%1-219 Highway safety U.S.Department of Tronsportat)on Federal Ht9hwaY Administration Evaluation November 1981 Procedural Guide Non-Accident- Based Project oEvaluation 4 Accident-Based Program + HIGHWAY SAFETY EVALUATION + Project Evaluation Evaluation + o o Administrative Evaluation o FOREMORD This Procedural Guide describes procedures for evaluating highway safety programs and projects. It should be beneficial to State and local engineers and other professionals involved in eval uation. The objectives of this Guide are to describe how to: 1. Select appropriate measures of effectiveness and efficiency to perform evaluations by using either accident data or alternate measures of hazard reduction. 2. Perform an evaluation of implemented safety improvements to gauge their effectiveness and efficiency and to use the results in recommending improvements for other safety or operational problems. 3. Describe and guide the organization and management of evaluation process (es) for providing feedback on the effectiveness of safety programs to the planning and implementation components of the Highway Safety Improvement Program. 4. Perform program effectiveness and administrative evaluations. The Guide was prepared by Goodell-Grivas, Inc. Mr. David Perkins was the Principal Investigator. !~r. Rudolph Umbs is the Implementation Manager. Additional copies of the Guide can be purchased from the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. Rqw Directo , Office of Developwnt b Federal Highway Administrate on NOTICE This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof. The contents of this report reflect the views of the Office of Development of the Federal Highway Administration, which is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official policy of the Department of Transportation. This report does not constitute a standard, specification, or regulation. The United States Government does not endorse products or manufacturers. Trade or manufacturer’s names appear herein only because they are considered essential to the object of this document. TABLE OF CONTENTS Description Page Introduction .........................................................1 History of the Highway Safety Improvement Program. ...................1 Framework of the Highway Safety Improvement Program. .................2 Highway Safety Improvement Terminology ...............................2 What is Evaluation?...................................................5 Why Evaluate? ........................................................6 Management Issues....................................................7 Procedural Guide Organization and Use ................................9 Accident-Based Project Evaluation ...................................l4 FUNCTION A- Oevelop Evaluation Plan ...........................l6 FUNCTION B - Collect and Reduce Data ...........................62 FUNCTION C - Compare Measures of Effectiveness (MOE ‘s).........73 FUNCTION D - Perform Statistical Tests ........................lO9 FUNCTION E - Perform Economic Analysis ........................l17 FUNCTION F - Prepare Evaluation Document ation .................l3B FUNCTION G - Oevelop and Update Effectiveness Oata Base. ......147 Non-Accident-Based Project Evaluation ..............................l55 FUNCTION A - Oevelop Evaluation Plan ..........................157 FUNCTION B - Collect and Reduce Non-Accident Data. ............194 FUNCTION C - Compare Non-Accident Measures of Effectiveness (MOE's) ..........................................ZOO FUNCTION D - Perform Statistical Tests ........................2O9 FUNCTION E - Perform Economic Analysis ........................233 FUNCTION F - Prepare Evaluation Documentation. ................240 FUNCTION G - Develop and Update Intermediate Effectiveness Data Base ........................................245 Program Evaluation .................................................251 FUNCTION A - Develop Evaluation Plan ..........................253 FUNCTION B-Collect and Reduce Data ..........................283 FUNCTION C - Compare Measures of Effectiveness (MOE ‘s)........290 FUNCTION O - Perform Tests of Significance ....................294 FUNCTION E -Perform Economic Analysis ........................3l6 FUNCTION F - Prepare Evaluation Document ation .................324 FUNCTION G - Develop and Update Effectiveness Data Base. ......329 i TABLE OF CONTENTS (CONTINUED) Description ~ Administrate re evaluation ......................................331 References .....................................................346 Appendix .......................................................351 Glossary of Terms ..............,...........................351 Statistical Tables .......................................J.361 The t-distribution for l-tail test ....................36l The t-distribution for 2-tail test ....................362 The X2-distribution for 2-tai 1 test ...................363 The z-distribution for 1- and 2-tail tests. ...........364 The F-distributi on ....................................365 Short Tables of Random Numbers. ............................367 Interest Factors for Annual Compounding Interest. ..........371 Safety Improvement Project Codes, Descriptions and Service Lives Used in Effectiveness Evaluation ..................384 Data Forms and Worksheets ..................................385 ii LIST OF FIGURES m ~ 1. Highway Safety Improvement Program at the Process Level. .........3 2. HSIP Subprocesses ..........................................+.....4 3. Evaluation Component inthe HSIP ................................l2 4. Sample Project Purpose Listing ..................................22 5. Sample Project Card File ..............-.-.......................24 6. Project Sampling Strategy .......................................26 7. Sample Objective and MOE Listing ................................3l 8. Before and After Study With Control Sites .......................33 9. Before and After Study With Control Sites (Trend Analysis). .....34 10. Before and After Study. .........................................36 11. Before and After Study (Trend Analysis ).........................37 12. Comparative Parallel Study ......................................38 13. Before, During and AfLerStudy . .................................4O 14. Assumed Change In MOE’s Before and After Project Implementation .42 15. Trends in MOE Values Over Time. ..........-..-...................42 16. Regression-To-The-Mean Influences on NOE’S ......................42 17. Experimental Plan Selection .....................................43 18. Sample Data Requirements Form. ..................................48 19. FUNCTION A Example Data Project Purpose Listing .................52 20. Project Sampl ing Worksheet For FUNCTION A Example (Multi-lane, Non-freeway Projects). .............................54 21. Project Sampl ing Worksheet For FUNCTION A Example (Two-1ane, Non-Freeway Projects) ......-.........................55 22. FUNCTION A Example Objective and MOE Listing ....................56 23. FUNCTION A Example Data Requirements Listing ....................58 . 111 m Page 24. Sample Accident Summary Table ...................................68 25. Sample Exposure Worksheet .......................................68 26. MOE Oata Comparison Worksheet ...................................74 27. 11lustration of MOE Data Comparison Worksheet For Before And After With Control Sites Study Plan .........................75 28. 11lustration of MOE Data Comparison Worksheet For Before And After Study Plan ............................................75 29. Illustration of ME Data Comparison Worksheets For Comparative Parallel Study Plan .................................76 30. 11lustration of MOE Oata Comparison Worksheet For 8efore, During and After Study Plan.... .........................76 31. Linear Regression Summary Table .................................84 32. Sample MOE Oata Comparison Worksheet ............................94 33. FUNCTION CExample #l Worksheet.. ...............................96 34. FUNCTION CExample #2 Worksheet. ................................g8 35. FUNCTION CExample #3 Worksheet ................................lOO 36. FUNCTION C Example #4 Worksheet ................................103 37. FUNCTION CExample#5 Worksheet ................................lO6 38. The Distribution of the Differences Between the Mean Values Of Random Samples ..............................................111 39. Probabi 1ity of a Type I Error ..................................111 40. Probability of aType II Error .................................111 41. Poisson Curves .................................................ll4 42. Sample B/C Analysis Worksheet ..................................129 43. Sample C/E Analysis Worksheet ..................................l33 44. Evaluation Study Materials Check list...........................l4O 45. Final Report Form ..............................................142 46. Estimated Accident Reduction Table .............................l5O iv m & 47. Accident Reduction Forecasts Used By Mississippi State Highway Department .............................................151 48. Accident Reduction Forecasts From Evaluation of Criteria. ......152 49. Effectiveness Data Base