The Braess paradox in mechanical, traffic, and other networks

We examine a network of strings and springs that exhibit counter-intuitive behavior. When a support string is cut, the load rises instead of falling. Our experimental. and theoretical, results lead to some general qualitative conditions for the existence of this paradoxical behavior, including effects of nonideal and nonlinear components. A simple procedure is given for doing a classroom demonstration of this behavior. This behavior is analogous to the well-known Braess paradox in traffic networks and also has (not, well known) analogs in electrical, hydraulic, and thermal networks. Some new insights into the traffic paradox are gained from a study of the mechanical paradox. (C) 2003 American Association of Physics Teachers.