A safety system for large and long over-the-road vehicles, such as a tractor semitrailer rig, having wheels mounted remotely from the vehicle's cab. A conventional airborne sound receiving microphone is mounted within a mechanical vibration damping housing at the bottom of the vehicle body near and aimed at the remote wheels to receive sounds from that area of the vehicle. The mounting and housing are constructed to prevent or greatly lessen mechanical vibration and sounds from reaching the microphone through the vehicle body. A communication cable runs from the microphone and housing to the cab and is connected through an amplifier to a speaker provided inside the cab. While the vehicle is being driven, the speaker reproduces a significant portion of the airborne sound received by the microphone within the cab. The system produces as background noise in the cab the sounds from the rear wheel area of the vehicle and allows the driver to note and react to changes in such noise as may result from a flat tire or other problem.