Planning and design of evacuation networks is both a complex and critically important problem for a number of emergency situations. One particularly critical class of examples concerns the emergency evacuation of chemical plants, high-rise buildings, and naval vessels due to fire, explosion or other emergency. The problem is a highly transient, stochastic, nonlinear, integer programming problem and previous methodologies utilizing queueing network models have proved useful in the design of emergency evacuation plans. We enhance this class of queueing network models by adding state-dependent queueing models to capture the nonlinear effects of increased occupant traffic flow along emergency evacuation routes. A mean value analysis algorithm and computational experience of the methodology illustrates our model's usefulness for this class of network design problems.