In the European Union (EU) and in Germany the transport sector is the only sector with increasing CO₂ emissions (in the EU by about 32 % and in Germany by about 1 % since 1990). Especially in road freight and air transport a further strong increase is forecasted. In the transport sector this might be impeded by avoiding transport (accepting a lower economic growth), shifting modes or in optimizing logistics. Especially the second is mentioned to be an adequate solution to meet the increasing demand for transportation and reducing CO₂ emissions simulatneously. It is often stated, that combined transport (mainly truck-train-truck) might be a very CO₂ efficient mode. In this article a Logit-Model (based on a survey of 500 German forwarders) is used to determine mode shift potentials of hauliers. The main factors of influence depending on the service provision of the transport modes are frequency of combined transport services, speed, and costs. For an estimation of the corresponding impact on the mode shift and thus potentials of CO₂ emission reductions two policy instruments are empirically tested: a further increase of the performanc ... mehre-based heavy vehicle fee (LSVA-Maut) and a hypothetical speeding up of the average speed in freight rail transport to 80 km per hour. Although the modal shift is rather high in the last policy simulation, the impact on CO₂ emissions is still small.