For evaluating ITS (Intelligent Transportation Systems) applications, microsimulation is becoming a more and more useful tool. In the evaluation process, one of the most important steps is the safety analysis. For such work, classical microsimulation outputs give some helpful information which are not sufficient for an accurate analysis in many cases. Nevertheless, the microscopic level of traffic description offers the possibility of knowing the relative position of the vehicles, their speed and deceleration. This paper will explain how a safety indicator can be calculated with these different parameters. This safety indicator is used in a ramp metering case study to illustrate the utility of such output for a safety analysis. This indicator is limited to the rear-end collision probability and gives therefore no information on crossing trajectories conflicts like in junctions.