I Comparing the 1985 HCMand the ICU Methodologies

Since the introduction of the 1985 High way Capacity Manual,’ there has been much discussion concerning its application. This is especially true in Southern California, where most government agencies and consultants have not yet agreed on a methodology for calculating signalized intersection capacity and level of service (LOS). Current methodologies include the 1985 Highway Capacity Manual (HCM), intersection capacity utilization computation (ICU), critical lane analysis, and, in some cases, Circular 212.2 This paper has been written to present arguments to a recently established committee within the Riverside-San Bernardino ITE Section. This committee was formed to address differences in the current methodologies used within the area. This paper compares the HCM and the ICU methodologies, which are the most widely used and the most controversial. Each methodology is briefly explained, and the deficiencies and advantages of each are identified. The methodologies are then compared and discussed, and the resulting differences in the determination of LOS are examined.