The purpose of this study was to quantify the effects of increasing the number of collision avoidance system alerts presented through a haptic driver seat on drivers’ response performance. Twenty-four participants performed specific driving maneuvers in response to one, three, or seven haptic seat alerts while they drove an instrumented vehicle. Participants verbally identified the alerts after executing a maneuver. Results show that drivers made the correct driving maneuver in response to the alerts. This was likely because of the strong stimulusresponse compatibility designed into the haptic seat. As predicted by Information Theory, drivers’ mean manual response time to the alerts significantly increased, and their verbal response accuracy significantly degraded, as the number of alerts increased. A three-alert haptic seat approach is recommended providing specific design requirements are met