These data are measurement time series collected onboard multiple mobile monitoring vehicles. The data are at a high time resolution (seconds to minutes). This dataset is associated with the following publication: Lin, M., G. Hagler , R. Baldauf , V. Isakov , and A. Khlystov. The Effects of Vegetation Barriers on Near-road Ultrafine Particle Number and Carbon Monoxide Concentrations. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 553: 372-379, (2016).