Analytic queueing model for ambulance services
  We present predictive tools to calculate the number of ambulances needed according to demand of entrance calls and time of service. Our analysis discriminates between emergency and non-urgent calls. First, we consider the nonstationary regime where we apply previous results of first-passage time of one dimensional random walks. Then, we reconsider the stationary regime with a detailed discussion of the conditional probabilities and we discuss the key performance indicators. 
Pedro A. Pury
stat.AP