Counterflow in Evacuations
  It is shown in this work that the average individual egress time and other performance indicators for egress of people from a building can be improved under certain circumstances if counterflow occurs. The circumstances include widely varying walking speeds and two differently far located exits with different capacity. The result is achieved both with a paper and pencil calculation as well as with a micro simulation of an example scenario. As the difficulty of exit signage with counterflow remains one cannot conclude from the result that an emergency evacuation procedure with counterflow would really be the better variant. 
Tobias Kretz
physics.soc-ph cs.MA