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PIARC TC C.2.3: Cost-Effectiveness of Safety Measures and Allocation of Resources. State of Michigan Time of Return Safety Calculation. Larry E. Tibbits Michigan Department of Transportation Kuala Lumpur, Malaysia. T ime o f R eturn (TOR). It is one type of cost benefit tool
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PIARC TC C.2.3:Cost-Effectiveness of Safety Measures and Allocation of Resources State of Michigan Time of Return Safety Calculation Larry E. Tibbits Michigan Department of Transportation Kuala Lumpur, Malaysia
Time of Return (TOR) • It is one type of cost benefit tool • Estimates benefits (reducing crashes/injuries/deaths) • Output: the number of years required to recover the safety investment • Based upon Roy Jorgensen’s report on Highway Safety Improvement Criteria
Why Use TOR • Federal Highway Safety Improvement Program requires that we invest safety dollars where they are needed most – where we get the greatest return • Helps prioritize competing safety projects • Verifies how the safety fix matches the demonstrated safety problem
Crash Data • Crash type • Number of crashes • Property damage only + minor injury (B, C) • Number of A injuries or number killed (people) • Each incident is one crash
TOR Components • Estimated costs of deaths and injuries from U.S. National Safety Council (http://www.nsc.org/) • Estimated benefits resulting from reducing crashes • Traffic volumes • Reduction in fatalities and A injuries combined • Reduction in minor (no A injuries or fatalities) crashes
TOR Components • Q factor to blend the impact of fatalities and A injuries • Estimated project costs • Number of years of crash data used (3-5) • Area Factor - Urban, rural, and between
The Calculation • Roy Jorgensen's Formula BTOTAL = ADTa/ADTbx/ (QxR1+(PDOCOSTxR2)) • BTOTAL = Total benefit in dollars over years used • ADTa = Average traffic volume after the improvement (assumed) • ADTb = Average traffic volume before the improvement
The Calculation (Continued) • R1 = Reduction in fatalities and A-injuries combined • R2 = Reduction in minor (no A-injuries or fatalities) crashes • Q = [FATCOST+((I/FxINJCOST]/1+(I/F]
Thank You http://www.michigan.gov/tands