ABSTRACT
The accessibility of health care services formed a basis for the earlier development of hospital districting patterns. If attention is focused on finding an adequate measure of accessibility, however, it is apparent that a number of potential difficulties have been ignored. Patients pay for accessibility costs in terms not only of money but also in time, discomfort and many other factors. One convenient method of calculating the minimum journey times, quickest paths and isochrones is based on the notion of a time surface. It is instructive before proceeding with other technical issues to visualise how a variable accessibility could influence hospital choice behaviour as seen through the eyes of the patient. The districting patterns described depend on an analogy between the network and a surface on which velocities change smoothly between points. Such generalisations are often adequate for a broad understanding of the basic forces influencing the locations of health care facilities.
