A practical methodology for ambulance location

Abstract

An ambulance location system was created for the British Co lumbia Provincial Ambulance Service. It was applied in the Capital Regional District (an area of about 937 square miles). The system helps administrators locate ambulances to improve response to calls.

The system consists of three parts: a means to reduce data to manageable proportions, a P-Median model for the determina tion of rough locations, and a computer simulation model for fine tuning of locations. The system worked well. The method of data reduction proved both practical and efficient. The rough locations provided by the P-Median model provided an excellent starting solution. The simulation model was shown to be ac curate in comparison with actual Capital Regional District data. The model was used with confidence to do a number of useful experiments concerning optimal ambulance locations and system response to changes in demand levels.

The validated system was used to answer many "what if" ques tions such as those that follow:

Are vehicles located in the best manner?

If we move one unit to reduce complaints from area A, how will this affect service in area B?

If we get more units, should we locate them incremen tally or would it be better to relocate all bases?

How much can we hedge against expected future demands?

How should we space shifts?

How should we determine the number of crews per shift?

Keywords

discrete simulation linear regression P-Median model shortest route algorithm

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References

Chaiken, J. and Larson, R. "Methods for Allocating Urban Emergency Units: A Survey." Management Science 19 (December 1972).

Church, R. and Revelle, C. "The Maximal Covering Location Problem." Papers of the Regional Science Association, Vol. 32 (Fall 1974).

Fitzsimmons, J. "A Methodology for Emergency Ambulance Deployment ." Management Science 19 (February 1973).

Kolesar, P. and Blum, E.H. "Square Root Laws for Fire Engine Response Distances." Management Science 19:12 (August 1973).

Revelle, C.S. ; Marks, D. ; and Leibman, J. "An Analysis of Private and Public Sector Location Problems." Management Science 16 (1970).

Revelle, C.S. and Swain, R. "Central Facilities Location." Geographical Analysis 2 (January 1970).

Revelle, C.S. ; Toregas, C. ; and Falkson, L. "Applications of the Location Set-Covering Problem." Geographical Analysis 8 (January 1976).

Savas, E. "Simulation and Cost-Effectiveness Analysis of New York's Emergency Ambulance Service." Management Science 15 (August 1969).

Swoveland, C. ; Uyeno, D. ; Vertinsky, I. ; and Vickson, R. "Ambulance Location: A Probabilistic Enumeration Approach." Management Science 20:4 (December 1973).

10.

Toregas, C. and Revelle, C.S. "Location Under Time or Distance Constraints." Papers of the Regional Science Association 28 (Fall 1972).

11.

Toregas, C. and Revelle, C.S. "Binary Logic Solutions to a Class of Location Problems." Geographical Analysis 5 (April 1973).

12.

Toregas, C. ; Swain, R.W. ; Revelle, C.S. ; and Bergman, L. "The Location of Emergency Service Facilities ." Operations Research 19 (October 1971).

13.

Uyeno, D. ; Seeberg, C. ; and Vertinsky, I. "An Ambulance Location System and Its Application to the Capital Regional District." Report to the Capital Regional District. Vancouver , Canada, (1981).

14.

Whitaker, R.A. "An Algorithm for Estimating the Medians of a Weighted Graph Subject to Side Constraints." Ph.D. dissertation. University of British Columbia, Vancouver, Canada (March 1971).