Variational principles in the analysis of traffic flows. (Why it is   worth to go against the flow.)
  By means of a novel variational approach and using dual maps techniques and general ideas of dynamical system theory we derive exact results about several models of transport flows, for which we also obtain a complete description of their limit (in time) behavior in the space of configurations. Using these results we study the motion of a speedy passive particle (tracer) moving along/against the flow of slow particles and demonstrate that the latter case might be more efficient. 
Michael Blank (IITP, Moscow, Russia)