The purpose of the reflectance sensors are to measure how far the AEV travels as it moves along the track. They are located on the wheel board. With a single infrared LED and a small photo-transistor on the red board, these sensors are used to detect each rotation of the wheel. This detection is caused by a reflective tape positioned on the wheel. Each time the wheel spins the reflective tape passes by the sensors and records and converts the rotations into marks. The wheel has a circumference of 3.9 inches. The conversion from marks to distance traveled is 3.9 inches per 8 marks or 0.4875 inches/mark calculating the distance traveled by our AEV. The reflectance sensors are important for using the commands goToRelativePosition(), goToAbsolutePosition(), getForwardsTotal(), getBackwardsTotal(), and getTotalMarks().