Transportation safety is of great concerns in our daily life. Both passive safety systems (such as seatbelt) and active safety systems (such as adaptive cruise control, i.e., ACC) have been proposed to reduce traffic accidents, especially in mitigating severity of an accident. As there are a variety of factors that lead to road traffic crashes, this project focuses on analyzing the traffic crash database and discovering the contributing factors for severe crashes, including incapacitating and fatal crashes, induced by speed-related crashes. The General Estimates System (GES) crash database from 1997 to 2005 has been explored. The influential factors, such as different scenarios of lighting environment, weather conditions, and road surface situation are investigated. The effects of ACC, as an example of active safety systems, have also been assessed.