Motor vehicles have been associated with high levels of trace metals in urban soils and the metals are mostly emitted though exhaust emissions, brake pad and tire abrasions. This study reports the levels of arsenic in roadside soils obtained from the surface at a depth of 0-5 cm in the Dares Salaam city which has the highest average daily traffic density in the country. The soils samples were collected at 1 m, 5 m, 15 m, 35 m, 50 m and 150 m distances from the road edge at each sampling site. Results showed that roadside soils were contaminated with arsenic and its levels ranged from 0.03 - 0.65 ppm (mean = 0.23 ppm). The amount of arsenic in the soil at each site decreased exponentially with increasing distance up to 35 m distance from the road edge. The Analysis of Variance (ANOVA) test showed that average arsenic levels in the soils varied significantly with study sites (F = 4.14, p = 0.01, n = 5) while the linear regression between average arsenic in all soil samples and average daily traffic density was statistically insignificant (r2 = 0.47, p = 0.21, n = 5). However, the observed spatial distribution of arsenic with increasing distance from the road edge strongly suggests that arsenic levels above background level in the study sites owe its source from traffic emissions.