The main objective of this study was to apply, evaluate and improve the methodology for testing the effect of active safety functions in critical scenarios (“Handbook of test method for Active Safety Systems”) which is under development in the FICA 2 project, by means of giving the handbook to an expert user (in this case the test leader at VTI) along with a set of study goals. However, at an early stage the project group realised that the version of the handbook then available was too abstract to just apply, i.e. it could not just be handed over to an expert user along with a set of study goals in order to produce a complete study. Instead, a joint study design effort took place in order to design a study which addressed a set of key research questions important to the evaluation of active safety functions in driving simulators, the implementation and results of which could be used for evaluation and improvement of the handbook. The research questions centred around the fact that many experimental studies use repeated lead vehicle braking events to study the effects of Forward Collision Warning (FCW) systems. However, in light of recent naturalistic driving research on how these events actually happen, it can be argued that this type of experimental design lacks result validity in terms of generalizability to the real-world emergency braking scenarios studied in the naturalistic driving studies. At least, a number of methodological questions on driver response and behaviour in the experimental studies need to be clarified before such generalization can take place. The main focus of the study was therefore to examine whether the presence of an FCW system affects driver response times in emergency braking scenarios, and if that effect is moderated by repeated scenario exposure. Furthermore, many studies evaluating FCW use distraction tasks to mask the critical lead vehicle braking event, though recent analysis has shown that the effect of distraction tasks which load working memory is highly correlated with initial time headway at task onset. Drivers spend more time on distraction tasks if initial time headway is larger, and vice versa. This effect has not been studied for visual distraction tasks. Therefore a second objective of the study became to examine whether initial time headway at visual distraction task onset affects driver response time in emergency braking scenarios, and whether that effect is moderated by repeated scenario exposure and/or FCW presence. To address the research questions, a critical lead vehicle braking scenario and an FCW system was developed and pilot tested in Saab’s fixed based driving simulator in Trollhättan. After piloting, the scenario was implemented in VTI’s moving base simulator in Linköping, and the effects, of FCW presence, two different initial time headways at visual distraction task onset and repeated scenario exposure, on driver response times were examined.