Like vision, adequate hearing helps ensure safety on the road for any driver. But, it is essential for a CMV operator whose vehicle is larger, less maneuverable and requires a longer distance to stop. External sounds, such as horns, emergency sirens or other signals warn of potential dangers or hazards. Adequate hearing allows the driver to react to these warnings in advance, before the hazards become visible. The driver must also recognize and interpret any noises in the vehicle.