Traditional crowd simulators are based on a simple numerical analysis of inputs such as the positions of people and structures; they do not consider leadership. Since leaders (in terms of evacuations) are present in many real-world situations, the validity of evacuation simulations can be increased through their introduction. We assess the results of a real-world evacuation experiment to develop more realistic scenarios for simulation. The simulations produced by the improved scenarios are found to closely mimic the experimental results. This work shows that scenario-based agent systems such as FlatWalk and FreeWalk offer excellent promise in simulating evacuations more realistically.