ABSTRACTBoth, the capability of a transport system to grant access to a destination and a traveller’s ability to utilize its opportunities can be distinguished in objective and subjective factors. The paper analyses the potential for objective accessibility factors to explain mobility behaviour. In more detail, the paper (i) quantifies the explanatory power of objective factors of the transport system (supply-side) for mode choice decisions and (ii) analyses if these supply-side factors, as well as objective factors of the traveller (demand-side), affects the level of multimodality among Austrian employees. Following this approach, the paper estimates mode choice models that only consist of trip features and accessibility factors. The final model reaches a high explanatory power and includes the individual transport mode availability, travel time, travel cost, public transport service quality and the car parking situation. The model allows simulation, which estimates the modal shift with respect to adaptations of the accessibility factors. Car travel time is the variable impacting mode choice decisions the most; this suggests a push-strategy when aiming to make the transport system more sustainable. Additionally, we show that both transport demand and supply factors, but most of all their combination can explain multimodal travel behaviour, i.e., whether or not a person uses more than one transport mode within one week. The explanatory value increases significantly if one also considers mobility tools. The variables explaining multimodality best are ownership of a bike and a PT season card as well as the public transport network density.