The minimization of travel effort as a delineating influence for urban hospital service areas.

Using a study population of 16,080 live births occurring to residents of Baltimore City in 16 hospitals in 1969, this research measured the existing flow of these patients against the flow "expected" in an optimal accessibility model (where each birth would occur at the hospital with the shortest travel time to the residence of the mother). The results of the study indicate that there is a general pattern of distance minimizing in travel for hospital admission with 50 per cent of the births occurring to women who travelled to one of the four closest hospitals of the 16 alternatives. However, a surprisingly large proportion (20 per cent) of the study population exhibited extreme spatial inefficiency by traveling to those four hospitals of the 16 alternatives which were farthest from their residence. A stepwise regression analysis identified five variables which best explained variation in the spatial efficiency of these urban obstetrical patients: low hospital occupancy, high total hospital admissions, average extra travel time potential (a measure of the difficulty of "spatial choices" facing patients depending upon the location of their residence with respect to the alternative hospitals), race, and the importance of the hospital's obstetrical service (a ratio of births to total admissions).