One of the essential parameters in signal timing, split is the most important variable, particularly at critical intersections where traffic congestion often occurs. There have been previous methods, in which optimum split is calculated in proportion to the critical traffic index. The problem is that determined split using these methods does not necessarily minimize the total delay time for all approaches of an intersection. In this paper, a new method of determining optimum split which satisfies this condition is proposed. In order to evaluate the validity of this approach, the experiments have been carried out, using a traffic flow simulator which simulates the behavior of each vehicle every second. These simulation experiments proved that the method presented here could decrease the queue length at the intersection, compared to the results using conventional methods which did not that efficiently.