Location of Multiple-Server Common Service Centers or Facilities, for Minimizing General Congestion and Travel Cost Functions

The authors propose a model for locating a fixed number of multiple-server service centers or facilities that may become congested. Customers arriving at these centers must wait in line until served. The locations of the facilities and the allocations of customers to them are chosen by the planner, so to minimize both travel costs and system-wide congestion (or queuing) at centers. All the customers arriving at the facilities must be served, up to a certain maximum line length. The travel cost in which customers incur is a function of the length of the trip to the facility, while the congestion cost at a facility is a general function of the number of customers waiting on line or being served at the facility. The resulting model is a nonlinear p-median formulation. A solution method for this nonlinear model is proposed, and computational experience is presented.