Abstract Nanoparticles generated from major roadways have a pronounced effect on human health, responsible for cardiovascular and respiratory problems, among others. In order to examine the effects of nanoparticles on human health, it is essential to know the factors/sources influencing both particle number concentration (PNC) and particle number distribution (PND). Real-world measurements were conducted close to an urban road located in the city of Bron near Lyon (France) over a flat terrain, where the dominant dispersion mechanisms stemmed from traffic and atmospheric turbulence. Roadside particle number concentration measurements were obtained using the Fast Mobility Particle Sizer™ (FMPS™) Spectrometer (Model 3091) at two different heights, as well as at different distances between source and sampling sites, ranging from 6.60 m to 330 m. Particles in the 5.6–600 nm size range were measured alongside a busy urban roadway. The effect of traffic volume, wind speed and direction, height above the road surface and distance from the source on both PNC and PND has been investigated. Results revealed that PNC increases significantly with an increase in height of less than 2.82 m above the road surface. Moreover, distance from the source and traffic volume is two correlated parameters. It has been shown that the highest concentration was observed at the distance nearest the road and vice versa. A bimodal daily average PND was found, with concentrated modes at 10.75 nm and then between 22.07 and 52.33 nm. Furthermore, PND was primarily influenced by nucleation and Aitken modes, as explanatory factors at the sampling site for the pollution produced from urban traffic.