Influencing travel behaviour is an important strategy in view of a number of transport-related societal challenges, on the one hand with regard to the capacity of the transport system and its financing in the face of increasing demand, but also in the pursuit of energy, urban development or health policy objectives.In addition to the long-term design of spatial planning (densification vs. urban sprawl) and the strategic expansion of transport services, the provision of targeted information (or other so-called "soft measures") and financial incentives are promising instruments for optimising mobility behaviour with regard to various target variables.In its Departmental Strategy 2016, DETEC has highlighted Mobility Pricing as an important solution approach that can contribute to ensuring the functionality and performance of the transport infrastructure, and in particular to smoothing out traffic peaks, in accordance with the causative principle and in a cross-modal manner. The strategy calls for the creation of the conceptual and legal basis for initial pilot applications. In the political discourse, the main obstacles are uncertainty regarding the concrete design of the pricing scheme and the distributional implications. From a scientific point of view, there is also considerable uncertainty regarding the reaction of transport users to transport- and time-specific price signals, as there are relatively few relevant studies in this area.In addition to private costs, the total cost of mobility includes external costs, e.g. in the form of infrastructure costs, congestion and emissions, which are borne by the general public and are therefore not sufficiently taken into account in the individual mobility choices. An economically efficient pricing system consists in the reflection of the total costs at the level of the individual road user, and thus leads to an actual cost truth in transport. Since an important part of external costs depends on the capacity utilisation of the transport system, the resulting price corrections vary over time and space and with the choice of transport mode.In a first step, the proposed project includes the further development of a modelling platform that allows to estimate the external congestion costs of mobility at the level of individual routes and distances and to supplement these with existing estimates regarding other external costs of transport. The second central element of the project consists of a randomised control trial in which the reaction of road users to the dynamic mobility prices calculated in the model is measured empirically using a smartphone app. As a possible substitute for financial incentives, the effect of information-based interventions, so-called "nudges", is also investigated.