The GSOM model (Generic second order model) is a macroscopic traffic model designed to take into account the dynamics of vehicle and driver attributes. It has recently been extended to the multimodal case. One prominent feature of the resulting multimodal GSOM model is that it distinguishes two flows: vehicular (car or public transportation) and passenger. The flow of pasengers is subordinated to the flow of vehicles. On the other hand, traffic on regional sized networks cannot be modelled with any great precision over very dense surface subnetworks of the regional network. Thus various approximate methods are being developped to address this difficulty, notably the MFD (macroscopic fundamental diagram) approach and bidimensional methods. The paper concentrates on the latter and aims first to develop a multimodal bidimensional model. In a second step the paper investigates how to interface the multimodal GSOM and the bidimensional models. At a regional scale the resulting model describes the structuring network (main roads, motorways, train tram metro lines...) following the GSOM methodology, and describes the flow on dense networks of small to medium capacity streets and lines as a bidimensional flow over a bidimensional medium.