The Federal Motor Carriers Safety Administration (FMCSA) is concerned that truck drivers' exposure to high levels of air pollutants and mobile air toxics for potentially long periods of time, may lead to acute and/or long term cognitive impairments as a result. The goal of this project was to compile existing information addressing the following question: Does exposure to diesel exhaust at levels found in cabs affect driver safety performance by affecting driver sleep, alertness, reaction time, fatigue levels, or judgment-making abilities? To determine whether such an effect exists, the Volpe National Transportation Systems Center conducted expert interviews to obtain insight into the question and searched the environmental and medical literature.