Vehicle pollution constitutes the major source of gaseous and particulate air pollution in urban areas. To limit particle mass emissions, and comply with European standards, diesel particle filters (DPF) have been largely used. However, certain after treatment devices increase ultrafine particle emission, and also affect NO2 emission. The first results show the importance of the cold start for the recent vehicles and that the frequency and duration of the DPF regeneration is a key point for particle emissions. In this poster two types of DPF are studied: catalyzed DPF and additive DPF.