The first attempts to directly detect alcohol in the driver's sweat and gear shift lever. A second system in the car uses a camera mounted in front of the driver to monitor eye movement. If the driver is drowsy it triggers the seat belt to tighten and this movement will hopefully snap the driver out of their drowsiness or prompt them to take a rest. A third system monitors the path of the vehicle to ensure it's traveling in a straight line and not weaving about the road, as is common with a drunken driver.