In order to support drivers to maintain a predefined driving speed, we introduce ChaseLight, an in-car system that uses a programmable LED stripe mounted along the A-pillar of a car. The chase light (i.e., stripes of adjacent LEDs that are turned on and off frequently to give the illusion of lights moving along the stripe) provides ambient feedback to the driver about speed. We present a simulator based user study that uses three different types of feedback: (1) chase light with constant speed, (2) with proportional speed (i.e., chase light speed correlates with vehicle speed), and (3) with adaptive speed (i.e., chase light speed adapts to a target speed of the vehicle). Our results show that the adaptive condition is suited best to help a driver to control driving speed. The proportional speed condition resulted in a significantly slower mean speed than the baseline condition (no chase light).