The Lexus Pre-Collision System (or PCS) is a combination collision detection and collision preparation system available on most Lexus models. The Pre-Collision System uses a millimeter-wave radar sensor to detect vehicles and other obstacles in your car's path, and calculates their speed and distance to determine if there is a risk of a collision. If the system determines that a collision is unavoidable the system prepares the car for an impact by tightening the front seatbelts and prepares the Brake Assist system to ensure that you have all the braking power possible if you need to slam on the brakes. On some models the vehicle can also detect if the driver is not paying attention to the road and provide an audible alert or tap the brakes to warn of an impending collision. On vehicles with the Lexus Adaptive Variable air Suspension (or AVS) the system also adjusts the air suspension to a firmer setting before a collision in order to improve chassis response and braking.