The object of the paper is to study issues related to reactive dynamic assignment in the context of communication, and specifically to analyze some impacts of information on reactive DTA (dynamic traffic assignment). New means of communication and new services will make instantaneous information on the network traffic state available to travelers. This will induce an instantaneous and long range interaction between all travelers /vehicles, with possible negative effects on the network traffic dynamics. In order to analyze such effects, the paper proposes the following: i) a dynamic multimodal macroscopic traffic flow model, for analysis an also prediction, based on the GSOM (generic second order model) approach; ii) a methodology for travel times estimation, compatible with the GSOM model; iii) a simple test setting for analyzing the impact of information on DTA. Preliminary results show that instantaneous travel time constitutes an information liable to induce unfavorable impacts and that predictive travel times yield better dynamics, because they induce a better coordination of global traffic dynamics.