Road traffic noise causes considerable disturbance and annoyance in exposed inhabitants. Particularly arterial roadnoise is significant environmental problem in many urban areas for higher traffic volume and car speed. Arterial roadnoise became the target of this investigation Seoul in Korea. Noise level were measured at four points that were basedon distance from roadside at the same measurement site and condition reported the National Institute of EnvironmentalResearch (NIER) in 1999. The average noise level (Leq,1h) of arterial road was 80.3 dBA at 5 m, 77.4 dBA at 10 m, 73.7dBA at 20 m, 70.9 dBA at 30 m. In case of the comparison between 1999 and 2008 s measurement values, noise levelis up about 1.5 dBA, traffic volume increase about 15.7%, car speed decrease about 8% compared with 1999 s measurementvalues. The relationship between 2008 measured values and predicted values using NIER Equation is lowunder 10 m at roadside. The influence range of arterial noise is calculated at 26 m by road noise limits in daytime. Incase of the comparison between traffic volume and noise level, relationship of equivalence traffic volume (Lightcar+10×Heavy car) is higher than other variables.