Traffic measurements and high-performance modelling of motorway emission rates

Within the framework of an extensive emission data validation experiment, the emission rates of the German motorway A 656 near Heidelberg have been determined using a new sophisticated emission model in combination with local traffic measurements. For this purpose, traffic parameters that are essential for the vehicles’ emission behaviour have been quantified by a measuring program that has been adapted to the special needs of a microscopic emission model. Traffic flows were recorded by automatic and manual counts. Fleet compositions were analysed by registration number evaluations. Speeds and accelerations were measured at different characteristic times and different road cross-sections. The road gradient was determined from precise altitude data. All experimental traffic data were used as input of a high-performance emission model and replaced traffic data from general databases step by step. The inclusion of all traffic and road data measured resulted in hourly daytime emission rates of 6000–11000 g km−1 h−1 for CO, 2500–4500 g km−1 h−1 for NOx, 350–600 g km−1 h−1 for NMHC and 150–280 g km−1 h−1 for PM. Uncertainty analyses show that the experimentally derived traffic data significantly reduce the errors of the modelled emission rates. The detection of traffic congestion situations by suitable monitoring methods is very important to the modelling of high-quality emission data for individual road sections.