Thesis (M.S., Psychology) | In a single experiment, I investigated the effects of displays, following distance, and lead vehicle size on a following driver's ability to detect and efficiently respond to decelerations of a leading vehicle. My aim was to compare a novel deceleration display to traditional brake lights in aiding following drivers in responding safely and efficiently to non-constant lead vehicle decelerations. The experiment found that both brake lights and a deceleration display improve the initial detection of lead vehicle deceleration as compared to no display or brake lights, but that the deceleration display also improved magnitude scaling of deceleration, as evidenced by higher correlations between lead and following vehicle trajectories, less extreme braking behavior, and higher minimum speeds. Theoretically, these improvements in the scaling of deceleration responses could increase the efficiency of traffic flow by reducing the tendency to over-react to lead vehicle decelerations, while still allowing drivers to maintain a safe gap. These results suggest that a deceleration display can afford more regulated deceleration responses in following vehicles, increasing both safety and efficiency of traffic flow.