The aim of the study was to determine the levels of selected trace elements in soils and in the common dandelion depending on the distance from a traffic route. The study was conducted in Warsaw near one of the main roads in the suburb of Ursynów. Samples for testing were taken from the 0–25 cm layer at sites located directly alongside the roadway and at a distance of 30, 60 and 300 m from its edge. The amounts of Pb, Ni, Cu, Zn and Cd in the soils were determined by the AAS method, after extraction in HCl at a concentration of 1 mol·dm−3, and in the aboveground parts and roots of dandelion plants after wet mineralization in a mixture of HNO3 and HClO4 by the AAS method. On the basis of the results obtained, it was shown that the concentrations of the tested metals, both in the soils and in the biomass of the test plant, were highest directly at the edge of the roadway and decreased significantly with the distance away from the road. This correlation indicates a significant impact of road transport on heavy metal levels in the environment bordering a traffic route. It was also shown that dandelion plants accumulate higher amounts of heavy metals in the aboveground parts than in the roots, and the heavy metal contents in the dandelion biomass were found to be significantly positively correlated with the amounts of these elements in the soils.