Evacuation drills are disruptive to business and cost money. Frequently the approach to evacuation drills is to carry out a ‘box-ticking’ exercise once a year that is the same as all the drills that have gone before. These drills are designed to minimise disruption and they tend to be successful – in that everyone leaves the building safely and moves towards the nominated assembly area. Little thought is given to the success measures beforehand or how evacuation might work in the more testing circumstances of a real emergency. Analysis and computer simulations can be used to test how evacuations should work under different conditions. This can be used to help design evacuation drills to get the most benefit so that the low cost of analysis can give a high Return-On-Investment in the drill. Finally the outcomes of this work can reduce the time taken to undertake drills saving time and money.