In urban areas, the time segment decision on the time-of-day of a timing plan for traffic signal control systems always depends on the practical judgments of traffic engineers. The procedure mainly rests on traffic engineers' experiences and lacks a set of objective appraisal criterion. If we use manual collection of 24-hour traffic volumes, its cost is quite considerable. This paper aimed to collect daily traffic volume by vehicle detectors on the road, along with a manual survey of the intersection peak-hour traffic volume, in order to estimate the traffic volume data in all directions of the coordinated intersections for the entire day by following the concept of flow conservation law. This paper adopted the K-means Clustering algorithm commonly used in statistics to determine the optimized signal time intervals over the 24-hour period according to the traffic characteristics at different times. Then, it set at least one hour for each time interval to complete the time interval allocation procedure. For each time interval, five settings of hourly traffic volume levels (50th percentile, 75th percentile, 85th percentile, 90th percentile and 100th percentile) were adopted as the interval representative volumes for establishing the timing plan. The timing optimization functions of the Synchro traffic control software and the TSIS traffic simulation software were used to calculate the average daily vehicle delay in cases of various time interval allocation results. Finally, this paper conducted an empirical analysis of the coordinated intersections in Taichung and Taipei cities. The findings showed that the performance of using the K-means algorithm to allocate the daily time-of-day time segments was better than the present plans in Taichung and Taipei cities. The analysis procedure in this paper could be used as the basic reference for traffic engineers in dividing the time of day break points by the results of performance comparisons.