The choice between public and private emergency ambulance services is generally based on histological experience within the community. No empirical evidence exists that supports an argument that either public or private emergency ambulance services are better, per se. On a macro level, this debate is based on the question of the role of government and the role of the marketplace in the delivery of public services and medical care, and the comparative efficiencies of public and private organizations. On a micro or community level, these philosophical concerns are supplemented with issues relating to protection of individual jobs and investments, upholding of community tradition, and maintenance of existing relationships. Other specific values that are considered include the role of profit and equity--fairness of coverage. A rational choice would be based on consideration of efficiency and effectiveness. The effectiveness of an emergency medical services system is primarily based on its ability to provide patients with the level of care that they need within a clinically appropriate time. Efficiency is the ratio between inputs and outputs. One factor that can increase efficiency is the availability of excess production capacity that can be used to provide emergency ambulance service, with a low marginal cost of adding this to the other functions. A rational model is intended to change the level of the debate to one that is less based on values, but it is impossible for a community to select an ambulance provider in a value-free environment.