This study was made to obtain information on the noise levels being emitted by vehicles currently using the highways of the State of Washington. The Washington State Highway Commission requested this study for guidance in proposing vehicle noise control legislation. The main controversy in states with existing comprehensive vehicle noise legislation has concerned trucks traveling on roads with posted speeds above 35 mph. The main thrust of our study is therefore concerned with this particular area, although data were also taken on automobiles and on roads posted at less than 35 mph. This study is unique in that the noise level and the speed of all vehicles were measured. In addition, all trucks over 10,000 lb were weighed. Our large body of data has been graphed in numerous ways to illustrate various aspects--including how the noise factor varies with speed, weight, and percentage of full load, etc. Some photographs of the trucks together with their noise data are also included.