  Using empirical data gathered on motorways in Germany, we follow a new
approach by further exploring response functions as a possible tool to study
traffic dynamics in motorway networks. We uncover the basic characteristics of
responses of flow and density to given signals and the capability of responses
to capture the correlation between these fundamental observables. Furthermore,
we uncover the potential use of responses to characterize traffic patterns. We
are able to demonstrate the differentiation of congestion patterns and the
determination of the propagation velocity of moving congestion.
