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Injury Severity and Total Harm in Truck-Involved Work Zone Crashes

Injury Severity and Total Harm in Truck-Involved Work Zone Crashes. Asad J. Khattak, Ph.D. Felipe Targa, MRP Carolina Transportation Program University of North Carolina at Chapel Hill. Work Zone Crash Problem. High societal cost operational disruptions

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Injury Severity and Total Harm in Truck-Involved Work Zone Crashes

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  1. Injury Severity and Total Harm in Truck-Involved Work Zone Crashes Asad J. Khattak, Ph.D. Felipe Targa, MRP Carolina Transportation Program University of North Carolina at Chapel Hill

  2. Work Zone Crash Problem • High societal cost • operational disruptions • property damage, injuries and loss of life • Fatalities and injuries from motor vehicle collisions (2000 in the US): • Increased rehabilitation & maintenance activities in future At $3 million/death = $2.5 billion/year

  3. Work Zone Crash Problem…cont • Other economic costs: • wage and productivity losses • medical and administrative expenses • property damage from non-fatal injury crashes • Severity of large truck-involved crashes • vehicle mass differentials • 16% of fatalities non-motorists (workers, pedestrians, and bicyclists)

  4. Literature • 2% - 3% of crashes work zone related • Crash rates increase in work zones • Rear-end and sideswipe crashes • Crash severity decreases • Large truck-involved crashes in work zones important contributors to fatalities • Gap: How do attributes of work zones affect safety?

  5. Research Objectives • Role of work zone attributes in harm & injury risk • Differences between truck-involved and non-truck-involved collisions

  6. Data (1) • HSIS + variables coded from police report narratives • New work zone variables in 2000 HSIS for NC: • WZ contributing factor • police officer opinion • Crash location • before, approach, adjacent WZ • WZ type • construct, maint, utility, moving • On-going work activity • WZ marked with warning • signs & cones

  7. Data (2) • Police report narratives • Crash Report Forms DMV-349 • Construction effect on • roadway capacity • Type of work being • done

  8. Dependent Variable • Two measures of crash severity: • Most seriously injured occupant in crash • ordinal measure—KABCO scale • Total harm in crash: Costs include quality of life • combines injury frequency & severity

  9. Modeling Methodology • Most seriously injured occupant • Ordinal categorical data  ordered probit model • Capture qualitative differences between different injury categories • Explore effects of WZ factors while controlling for non-WZ factors • Marginal effects for injury severity • Total harm (Semi-log OLS) • Cost data  OLS regression • Log-transform of cost avoids negative predictions & collapses range

  10. Modeling Methodology

  11. Results • Frequency analysis—Truck-involved collisions: • WZ activity was on-going (62%) & no traffic control device present (63%) • Two-way, divided, with median barrier (48%) & WZ construction type (82%) • Location of crash: before (20%) in approach area (34%), & adjacent (46%)

  12. Results • Models statistically significant—99% level: • F-tests for OLS models • Likelihood-Ratio tests for ordered probit models • Reasonable goodness-of-fit: • Adjusted R2s range from 0.293 to 0.343 for OLS log-transformed models • McKelvey & Zavoina pseudo-R2s range from 0.146 to 0.242 for ordered probit models

  13. Results • WZ-related variables coded from the DMV forms: • Roadway closed, detour opposing side • Increases cost by factor of 143% relative to other construction types • Marginal effects: Injuries increase by 38.5%, (minor injuries 9.5% higher, moderate 13.4%, severe 12.5%, and fatalities 3.2%) • Road closings in WZ are very risky esp. for truck-involved collisions • HSIS WZ-related variables: • Crash location adjacent WZ or transition area • Cost 33% (transition) and 23% (adjacent) more than before • 11.9% higher chances of injuries (adjacent)

  14. Results • HSIS WZ-related variables: • Two-way undivided roadways • 37% higher costs compared with two-way divided & protected (with median barrier) roadways • 19.1% higher chance of injury • Other HSIS variables associated with higher severity: • Higher posted speed limit • Presence of stop/yield/warning flashing signs-effect not causal

  15. Conclusions • Injury & harm associated with WZ attributes-given WZ crash • Multi-vehicle truck-involved collisions most injurious & harmful • trucks increase severity of occupants from other vehicles; smaller cars • Greater attention to (reducing high-risk factors identified will reduce their severity and associated costs, not frequency): • Road closings • Activity/work areas • Two-way undivided and two-way divided but unprotected configurations • Posted speed limits • Valuable information for developing WZ strategies intended to improve safety, especially in costly truck-involved collisions

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