Driving is a high-risk adventure which many enjoy on a daily basis. The driving task is highly complex, ever-changing, and one which requires continuous attention and rapid decision making. It is a task that is not without risk, where the cost to reach the desired destination can be too great – your life could be at stake. Driving is not without incidents. Rear-end collision is a common problem in the Swedish traffic environment, with over 100 police-reported individual incidents per year. The amount of rear-end collisions can be hypothetically reduced by introducing new technology in the driver’s vehicle, technology which attempts to improve the driver’s safety driving. This technology is called Advanced Driver Assistance Systems – ADAS. In this study two ADAS were evaluated in a driving simulator study: An Adaptive Cruise Control (ACC) which operates on both hazardous and non-hazardous events, and a Collision Warning System (CWS) which operates solely on non-hazardous events. Both of these ADAS function to guard against risky driving and are based on the assumption that drivers will not act in such a manner that they would willingly reduce the effectiveness of the system. A within-subjects simulation study was conducted where participants drove under three conditions: 1) with an adaptive cruise controller, 2) a frontal rear-end collision warning system ADAS, and 3) unaided, in order to investigate differences between the three driving conditions. Particular focus was on whether the two ADAS improved driving safety. The study results indicate that driving enhanced by the two ADAS made the participating drivers drive less safely.