During motor transport operation, elevated concentrations of solid particles are formed in the air over the roadway as a result of particulate matter emissions from vehicle exhaust gases, tire and road surface wear particles, background air pollution and other processes. The content of tire and road surface wear particulates in the air over the roadway, as it has been specified in the previously submitted materials of the Russian delegation, amounts up to 60% from the total percentage of solid particles (WP-29-160-39). This paper presents further research into this subject.