In the conventional evacuation planning process, evacuees are assigned to fixed destinations mainly on the basis of geographical proximity. However, the use of such prespecified destinations (an origin-destination table) almost always results in less-than-optimal evacuation efficiency because of uncertain road conditions, including traffic congestion, road blockage, and other hazards associated with the emergency. By relaxing the constraint of assigning evacuees to prespecified destinations, a one-destination evacuation (ODE) concept has the potential to improve evacuation efficiency greatly. To this end, a framework for the simultaneous optimization of evacuation traffic distribution and assignment is proposed. The ODE concept can be used to obtain an optimal destination and route assignment by solving a one-destination (1D) traffic assignment problem on a modified network representation. When tested for a countywide special event-based evacuation case study, the proposed 1D model presents substantial improvement over the conventional multiple-destination (nD) model and can potentially reduce overall evacuation time by more than 60%. More important, this framework can be easily implemented and its efficiency enhanced simply by instructing evacuees to head for destinations resulting from the 1D simulations run beforehand.