This research quantifies current sources of non-exhaust particulate matter traffic emissions in London using simultaneous, highly time-resolved, atmospheric particulate matter mass and chemical composition measurements. The measurement campaign ran at Marylebone Road (roadside) and Honor Oak Park (background) urban monitoring sites over a 12-month period between 1 September 2019 and 31 August 2020. The measurement data has been used to determine the traffic increment (roadside – background) and covers a range of meteorological conditions, seasons and driving styles, as well as the influence of the COVID-19 ‘lockdown’ on non-exhaust concentrations. Non-exhaust PM10 concentrations are calculated using chemical tracer scaling factors for brake wear (barium), tyre wear (zinc) and resuspension (silicon) and as average vehicle fleet non-exhaust emission factors, using a CO2 ‘dilution approach’. The effect of lockdown, which saw a 32% reduction in traffic volume and a 15% increase in average speed on Marylebone Road, resulted in lower PM10 and PM2.5 traffic increments and brake wear concentrations, but similar tyre and resuspension concentrations, confirming that factors that determine non-exhaust emissions are complex. Brake wear was found to be the highest average non-exhaust emission source. In addition, results indicated that non-exhaust emission factors are dependent upon speed and road surface wetness conditions. Further statistical analysis incorporating a wider variability in vehicle mix, speeds and meteorological conditions, as well as advanced source apportionment of the PM measurement data, will be undertaken to enhance our understanding of these important vehicle sources.