TRACTOR-TRAILER CRASHES IN INDIANA - A CASE-CONTROL STUDY OF THE ROLEOF TRUCK CONFIGURATION

Studies of the crash experience of tractors pulling multiple trailers have reached different conclusions concerning the relationship of truc k configuration to crash risk. A previous case-control study found a s ignificant increase in crash risk for double-trailer trucks in the sta te of Washington. The present case-control study was done of tractor-t railers crashing on Indiana interstates during November 1989-March 199 1. Controls were obtained for 25% of the crash sites and were all trac tor-trailers passing the crash sites during a traffic observation sess ion one to four weeks following a crash on the same day of the week fo r 30 minutes at the same time of day. Logistic regression identified d ay of week, time of day, urban/rural area, and specific highway as sig nificant predictors of controls' truck configuration. This model was a pplied to the cases to estimate the expected number of double-trailer cases. For all crashes combined, no increased crash risk was observed for doubles (Standardized Crash Ratio (SCR)=83). Doubles were signific antly underinvolved in multiple-vehicle crashes (SCR=74), crashes on d ry roads (SCR=61), and crashes on wet (other than snow, ice, or slush) roads (SCR=54). Doubles were significantly overinvolved in crashes on roads with snow, ice, or slush (SCR=153). Because truck configuration was highly associated with driver age and work operation attributes a mong trucks in crashes, the absence of control data on these potential confounders precluded definitive assessment of the intrinsic risk of multiple versus single-trailer vehicles. Copyright (C) 1997 Elsevier S cience Ltd.