The main purpose of this paper is to present a method for determining yellow time of left-turning traffic flow based on dilemma zone concept. The results of comparative analysis show that estimated yellow times obtained from the model proposed in this paper are much different from actual yellow times obtained from the field. Actual yellow times are considerably shorter than the estimated yellow time. These results would be very significant for signalized intersection networks in terms of improving traffic safety and traffic signal operation. A method for improving yellow time of left-turning movement by Intelligent Transportation Systems (ITS) is presented.