A simulation/assignment-based approach is introduced for evaluating the regionwide effect of signal preemption strategies for bus transit operations. The model addresses both the propagation and interaction of traffic with the bus operations as well as the routing behavior of drivers in response to the introduced preemption control. Furthermore, the need and feasibility of conducting this evaluation at the systemwide level is discussed and demonstrated. An example traffic network that includes Cermak Road in Chicago, Illinois, is used to demonstrate the applicability of the modeling approach.