Our aim is to develop Advanced Driving Assistance Systems (ADAS) which are suitable for all customers in all driving conditions. To achieve this goal, a new methodology was developed to characterize driving manner in each scenario by a mathematical model based on Naturalistic Driving Study (NDS) data. To represent the variety of driving manners, a new parameter named “aggressiveness” is introduced. By adjusting “aggressiveness”, the ADAS’ behaviour can be modified, matching natural driving behaviour in a wide range of operating conditions. This methodology is applied to model when drivers start to brake when approaching another vehicle that’s driving in the same lane. This model can be used to detect when a driver is not assessing a threat correctly by comparing his instantaneous driving behaviour with his normal driving behaviour.