Providing spatial decision support for rural public service facilities that require a minimum workload

One class of spatial problems is concerned with the location of facilities and the allocation of demand to them. A special case occurs in rural areas where a minimum workload may be needed to ensure the viability of a facility. Where a facility does not meet this threshold workload, demand may be reallocated from adjacent centres that exceed their thresholds. Decisionmakers traditionally have undertaken this reallocation process either by using optimising algorithms or by adopting subjective self-identified changes to the system. An algorithm, called ADJUST, has been developed to bridge these two approaches. Although ADJUST identifies a sequence of demand units to be reallocated that least increase the total distance travelled in the system, decisionmakers explicitly control the trade-off between meeting the workload threshold of a facility and the extra distance incurred in reallocating a demand unit to it. Such a supervised trade-off process is applicable to a broad class of geographic problems. We describe the strategies employed by a group of decisionmakers when they used ADJUST to reorganise area education authorities in Iowa, the implementation of the algorithm, and possible extensions to enhance its ability to support collaborative spatial decisionmaking processes.