Evaluation of emergency ambulance characteristics under several criteria.

A methodology and analysis are presented for evaluating response time characteristics of emergency ambulance systems. The methodology is based on a Monte Carlo simulation technique and a heuristic optimal-seeking technique for locating emergency ambulances under several criteria based on response time distribution. Optimization criteria include minimum mean system response time, minimum system fractile response time and minimum level-loaded response time. The evaluation methodology is applied to the metropolitan area of Los Angeles County. Ambulance response characteristics and loads are discussed in detail. From these results alternative dispatch polices can be evaluated. Complementing the analysis is a presentation of a sensitivity analysis and an analysis of existing ambulance sites. Unique to the methodology is the adaption of the heuristic optimal-seeking technique to include any of the three criteria and the effectiveness of the methodology for analyzing small or large ambulance systems.

Predicting demand for publicly dispatched ambulances in a metropolitan area.

A model to predict demand for publicly dispatched emergency ambulance service in Los Angeles County is constructed using 1970 census tract and land usage data and 1973 population and utilization data. Although data were not available for many communities within the county, results indicate that the mode, which uses four socioeconomic variables, can accurately explain actual variations in ambulance demand for individual communities in Los Angeles County and for larger regions within the county.

Level-load retrieval time: a new criterion for EMS facility sites.

A new optimization criterion for locating emergency medical care facilities, level-load retrieval time, is described and applied to Los Angeles County. Results are compared with those obtained by optimizing mean retrieval time. The new cirterion combines retrieval times from demand points served by each facility and patient load on each facility; it yields facility sets with average retrieval times 5 to 10 percent longer, but with much more uniform patient loads, than the sets obtained by optimizing mean retrieval time. The new criterion can be used as a complement to other planning criteria and may help reduce excessive demand on the emergency care services of overloaded facilities.