Submicron particle size distributions were obtained at a roadside site in Bristol over a three month period, alongside measurement of gaseous pollutants (CO, NO, NO₂ and NO­_x), PM₁₀ and traffic and wind data. Size distributions are broadly bimodal in nature with peaks at ~30 and ~100 nm in agreement with previous work.  There is an obvious rush hour peak in concentration on weekdays which is not present at weekends, but the overall shape of the distribution and mean particle diameter is similar. Correlation between hourly-averaged particle number concentration (PNC) and PM­₁₀ is weak, and between PNC and gaseous co-pollutants moderate, although the relationship may be affected by differential production rates for PNC and gaseous pollutants at high PNCs.