The evaluation of government programmes designed to prepare for future contingencies is an ongoing challenge for analysts and public managers. Despite significant focus in emergency management, the existing approaches have difficulty linking preparedness inputs to their effect on performance at future response operations. Adapting techniques from the analysis of technical systems, an approach for assessing response reliability – the likelihood that a response system will be able to deliver response capabilities at or above a specific level at a future incident – is described. The approach bases evaluation on the systematic assessment of the likelihood and consequences of events that would disrupt operations and reduce response performance. By doing so, it provides a clearer method for assessing the cost effectiveness of different preparedness policies and evaluating the performance of past investments in preparedness programmes.