This research aims to develop a road safety assessment index (RSAI) based on the safe system concept. This index can be used to rate and rank countries according to the effectiveness of the national road safety strategic plans; to monitor the progress towards a set target; and to suggest strategic solutions. To develop the RSAI, its thematic indicators are identified to cover safer road infrastructure and mobility, safer vehicles, and safer road-user behaviour. A sub model is developed for each thematic indicator, along with their individual indicators that can give a full reflection. The road assessment programme (RAP) is considered to identify the indicator of safer road infrastructure and mobility. For this, a procedure for extending the RAP methodology is developed and evaluated. The new car assessment programme (NCAP) of rating cars is chosen to identify the safer vehicle indicator. While seven indicators are selected to form the sub model of safer road-user behaviour. The chosen indicators are weighted and aggregated to form the RSAI's preliminary models. These models are evaluated through comparing with the rate of road fatalities, to decide the final form of the RSAI model. The results show the suitability of the RSAI model in assessing the road safety level, and in achieving its purposes.