Ultra-fine particles (UFP) prove to be highly suited to measuring in Fietsbalans. Measurements taken under similar weather conditions on various routes by bicycle have yielded large differences that are related to intensity and composition of motor vehicles. The sensitivity to the proximity of local sources, in particular motor vehicles, matches the traffic engineering nature of Fietsbalans. Effects of road layout and traffic circulation are therefore directly measurable. High peak values for ultra-fine particles are mainly caused by special vehicles (for instance builder’s cranes, refuse-lorries etc.), backed-up traffic, lorries, vans and the various types of moped.
On the basis of the measurements taken during Fietsbalans it is difficult to make statements relating to health effects of local air pollution. During his trip a cyclist is almost always more exposed to ultra-fine particles and PM2,5 than car drivers, particularly after a breath correction due to the effort expended. This exposure of cyclists may be influenced by the choice of routes. A lower degree of exposure will have a positive effect on health. The exposure can however not be translated into individual health damage. Moreover, the positive health effects of the cyclist’s exercise would have to be included into the equation as well.