Effects of Functional Separation and Low Levels of Blood Alcohol on the Response to Automobile Rear-Signal Information

Abstract

The experiment investigated the effects of functional separation of brake and turn-signals, and of low levels of alcohol intoxication on a driver's ability to detect and interpret rear-signal information presented on a model automobile in a laboratory setting. Twelve experienced drivers performed the laboratory task for one-hour sessions on five successive days. Three independent variables were examined in a randomized-block, factorial design. These consisted of two levels of model type, one with brake and turn-signals combined under the same lens, the other with brake and turn-signals under separate lenses, four levels of blood alcohol, .00, .02, .05, and .08%, and six levels of stimulus complexity, representing six types of rear-signal information. Response variables consisted of response errors and the latencies between the onset of the stimulus and both the onset of the response and the completion of the response. Results indicated that the response variables were not equally sensitive to the task and that performance was significantly affected by model type and stimulus complexity. Performance deteriorated with blood alcohol levels as low as .05% on the combined model and 0.8% on the model that separated brake and turn-signal lights. Results are discussed in terms of the stimulus-identification/response-choice components of the task, and in terms of optimal coding methods for rear signals.