This paper presents data for several tire/pavement interaction noise measurement problems present in passby tests. Two of these, the after peak and the difference of the passby maxima with direction of travel, have not been previously reported. The underlying causes of many of the problems are discussed. Probable interactions with current regulatory procedures on the overall vehicle passby levels are indicated. The need for much more precise site control is pointed out, especially with respect to atmospheric conditions which strongly affect the noise transmission path and with respect to the pavement texture.