PIARC TC C.2.3:

Cost-Effectiveness of Safety Measures and Allocation of

Resources

State of Michigan Time of Return Safety Calculation

Larry E. TibbitsMichigan 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