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ANALYSIS OF INJURY AND NON-INJURY CRASHES IN CALIFORNIA WORK ZONES

ANALYSIS OF INJURY AND NON-INJURY CRASHES IN CALIFORNIA WORK ZONES. Asad J. Khattak Department of City and Regional Planning University of North Carolina-Chapel Hill Aemal J. Khattak Department of Civil Engineering North Carolina State University Forrest M. Council

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ANALYSIS OF INJURY AND NON-INJURY CRASHES IN CALIFORNIA WORK ZONES

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  1. ANALYSIS OF INJURY AND NON-INJURY CRASHES IN CALIFORNIA WORK ZONES Asad J. Khattak Department of City and Regional Planning University of North Carolina-Chapel Hill Aemal J. Khattak Department of Civil Engineering North Carolina State University Forrest M. Council Highway Safety Research Center University of North Carolina-Chapel Hill

  2. Work Zone Crash Problem • 700 fatalities per year in the US • 24,000 injury crashes • 52,000 non-injury crashes • May increase due to increased rehabilitation & maintenance activities

  3. Literature • Work Zone crashes represent 2% - 3% of reported crashes • Crash rates increase in work zones Rear-end and sideswipe crashes • Crash severity decreases

  4. Research Objectives • Examine crash rates on major freeways before and during work zones • Examine change in crash severity • Examine effects of ADT, work zone length, duration, and location on crashes

  5. Data • HSIS database • 36 California freeway projects • Comparison sites were same locations in 1992/93 • Before work zone data: 1992 + part of 1993 • During work zone data: part of 1993 • Work zones included 0.8km on each end as “transition zone”

  6. Data Problems/Challenges • No volume counts during work zone period (thus assumed constant AADT) • Crashes had to be matched by both location and time

  7. Sample Characteristics • Av. work zone length: 7 km • Av. work zone ADT: 101000 veh • Total reported crashes: 8090

  8. Crash Rates/mvkm Rate Increase PDO + 23.8% Injury + 17.4% Total + 21.5%

  9. Modeling PDO and Injury Crashes • Four Negative Binomial models • Dependent variables: PDO & Injury crashes in before & during work zone time • Independent variables: ADT, Natural log of duration, Natural log of wk zone length, Urban location indicator, Exposure term

  10. Model 1 -- PDO Crashes, Before Work Zone

  11. Model 2 -- PDO Crashes, During Work Zone

  12. Model 3 -- Injury Crashes, Before Work Zone

  13. Model 4 -- Injury Crashes, During Work Zone

  14. Results • ADT - Significant, but effect is comparatively reduced during work zone on PDO & injury crashes • Work zone duration - Significant & effect is comparatively enhanced during work zone on PDO & injury crashes - Effect is greater on PDO crashes

  15. Work zone length - Affects both PDO and injury crashes, (but duration seems more important) - Effect is about the same on PDO & injury crashes • Urban location - Not significant • Exposure - Not significant (effect may be captured by ADT, duration, and length)

  16. Conclusions • To reduce work zone crashes, can reduce traffic, work zone length, & time duration • Shortening the duration seems more important than reducing work zone length or traffic • Shortening duration will have most effect on PDO crashes

  17. Needed Research • Effects of different traffic control schemes in work zones - Would require detailed information on traffic control phasing, signing, marking, etc. • Identification of innovative work zone strategies - Trucks in one lane, Fewer lane closures, etc. • Decreasing work zones and duration • Longer life pavements, etc.

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