This thesis describes a methodology for adding information about the preferences for new modes from external discrete choice models to exisiting transport demand gravity models. The methodology consists of 4 steps: (i) translation of deterrence functions towards discrete choice utility functions; (ii) linearization of non-linear translated utility functions, (iii) determination of factors to correct the scale of external models and (iv) the specification of the combined model. The thesis provides a case study related to "Urban Mobility as a Service" for the Eindhoven-Veldhoven area to show the practical validity of this methodology.