In previous literature, sound intensity has been used to quantify the strength of tire-pavement interaction noise sources very near an operating tire under non-driven, cruise conditions as measured on trailers or actual vehicles. In the current investigation, the relationship between such on-board sound intensity data and coast-by sound pressure levels measured 7.5 meters away from the centerline of vehicle travel were examined. When compared either in terms of overall A-weighted levels or 113 octave band spectra, these data demonstrate a strong correlation between the two types of measurements. Given this correlation, the sound intensity technique was then used to quantify the tire/pavement interaction noise for the driven tires of a passenger car under accelerating conditions such as those specified in the ISO 362/SAE 51470 or SAE 5986 passby noise procedures. These data indicate that in some cases, the strength of the tire-pavement noise produced under acceleration on an overall A-weighted sound pressure level basis can be as much as 9 dB higher than those measured under cruise conditions. This effect has been investigated for several different tires covering several different acceleration rates in the speed range from 48 to 80 km/hr. The results of this study are examined in detail with attention given to differences in performance between tires and to /exterior passby noise contributions.