Measurements of the amplitude of the detected envelope of man-made noise have been made at a frequency near 80 MHz, and the results presented in the form of amplitude probability distribution curves. The major contributing sources are the ignition systems of vehicles and measurement locations such as business areas, arterial roads, and suburban areas have been chosen to give a variety of conditions. Although traffic density is the major parameter that has to be taken into account, the pattern of traffic flow is also a contributing factor.