A case-control study was conducted in Long Beach, CA and Fort Lauderdale, FL to examine the relative crash risk associated with drivers’ blood alcohol concentrations (BACs). Data were obtained for drivers involved in 2,871 crashes of all severities. Two control drivers for each crash driver were sampled a week after the crash at the same location, on the same day of the week and at the same time of day. For both groups of drivers, a research team recorded observations, administered a brief questionnaire and obtained breath specimens for BAC measurements. Of the 14,985 sampled drivers who were potentially available for testing, 91.7% of crash drivers and 97.9% of control drivers provided breath specimens. When drivers who fled the crash scene are included in the number of potentially available drivers, the percentage that provided a breath specimen reduced to 81.3%. Relative risk models were generated with logistic regression techniques with and without covariates such as driver age, gender, marital status and ethnicity. The models without adjustment for the covariates show elevated relative risk beginning at 0.05 – 0.06% BACs with an accelerating increase in risk at BACs greater than 0.10%. With adjustment for covariates and bias due to missing data (nontested hit-and-run drivers, refusals, and incomplete responses), risk was elevated at a slightly lower BAC and the risk curve was steep. Statistically significant risk occurred at 0.04% BAC and small, non-significant elevations occurred at BACs closer to zero. Relative risk models were also produced for age groups and alcohol consumption levels. (Author/publisher)
Abstract