In order to develop and deploy advanced safety technologies, it is important to estimate effectiveness based on the system function or performance. Although various types of safety impact methodology (SIM) have been proposed to date, few SIMs can be applicable for actual system effectiveness estimation. In this study, a universal SIM (T-SIM) was developed and its validity was confirmed against field data. T-SIM uses the number of fatalities and casualties (fatal and nonfatal injury) that are expected to be prevented by the technologies rather than just collision/avoidance ratio because some of the safety technologies, such as collision mitigation system, can reduce the impact speed by brake application and thus may help reduce the number of fatalities and casualties. T-SIM consists of two parts: (1) accident pattern classification and (2) effectiveness estimation for each system. In the first part of the T-SIM, accident data from the National Automotive Sampling System - General Estimates System (NASS-GES) and Fatality Analysis Reporting System (FARS) were categorized by such variables as type of accident (e.g., head-on) and relation to the intersection. The categorized accident patterns enable users to choose the accidents for which the technologies may be effective. By using the same accident pattern database, users also can compare the effectiveness of different safety systems. In the second part of the T-SIM, accident patterns applicable to a particular safety system are selected from the categorized patterns. A driver-model and a vehicle-model can be applied, which allows users to examine the effect of system parameters and configurations. Through the validation process using a Electronic Stability Control (ESC) system as an example of advanced safety technologies, the estimated effectiveness by T-SIM was compared with that reported by a study based on field data . Although the accident databases are different, statistical analysis showed the effectiveness estimated by T-SIM is not significantly different from that by the field study and it was confirmed that the T-SIM can be used to estimate the effectiveness of other advanced safety technologies. Then the T-SIM was applied for a Pre-Collision System for the effectiveness estimation and further improvement. It was estimated that a PCS has high potential for reducing fatalities and casualties of rear-end accidents. In addition, it was also estimated that the PCS could be improved by changing such system parameters as warning, brake-assist and automatic brake timings.