Real driving emissions of cars, buses and trucks determined by Plume Chasing in Czechia: Fleet screening and intercomparison with other methods

, particle number (PN) and black carbon (BC) emission factors of light duty vehicles (LDVs), trucks, and city buses were investigated using Plume Chasing. The study was conducted in Czechia, focusing on the capital city of Prague. In total 402 distinct LDVs, 66 city buses and 948 trucks were measured. We found that 50% of the emissions come from 3-28% of the dirtiest vehicles, depending on pollutants, vehicle category and fuel. The most pronounced are BC emissions from diesel cars with just 3% of cars responsible for 50% of emissions. In this study, for the first time, different remote emission sensing techniques were compared with Plume Chasing in real urban driving. To achieve this, Plume Chasing measurements were performed at locations where Point Sampling and cross-road remote emission sensing (OPUS-RSE) were co-located. In addition, comparisons with Portable Emission Measurement Systems (PEMS) were performed for three different test LDVs and the three different remote emission sensing methods in real urban traffic. The comparison between the three different remote emission sensing techniques gives similar average emission factors for the three test vehicles and for the measured fleet. However, for individual measurements the emission factors can differ quite strongly. The individual Plume Chasing measurements deviate the least from PEMS results, likely because the measurement interval is longer when following the vehicle through different sections of road and engine states. For Plume Chasing, different recommendations are made based on the PEMS comparison, such as excluding downhill sections or sections with high emitting vehicles in front of the chased vehicle or in oncoming traffic.