Abstract Finding the utilization of a set of machines in a shop floor of a production system by the ratio delay method is a well-known practice in conventional time and motion studies. In this method, the desired reliability of the study is preset and subsequently the data are collected to achieve that reliability. I do not continuously review the reliability in this method while conducting the study nor do I measure the benefit-cost ratio of the undergoing study. In this paper, I describe a method to determine the utilization of a set of production facilities and continuously review the reliability achieved at the end of each survey period. The random observations about the machine status generate a utilization profile of a set of machines on a continuous time scale. Based on the benefit-cost ratio, this method provides us with an information as to when the study has to be stopped in a real time situation. The study is substantiated with a case study and an indication of further research.