The Reflectance sensors serve to automate the AEV’s functions, mainly how far the AEV travels at a given time. They are sensors which contain an infrared LED and a small phototransistor, which are attached next to the wheels of the AEV. They measure the how many marks, with each mark being 0.4875 inches, the wheels of the AEV travel. They function by measuring each time the sensor passes by the non-reflective part of the wheel, recording it as a mark. As a result, these sensors tell the AEV how far it should go, and when it should stop. This is an integral part of the autonomous part of the AEV, allowing it to run precisely without human supervision.