Sub-problem 3b: Operational Analysis of the Center Section of Krome Avenue (Class I or II Two-Lane Highway Facility)

The procedures given in HCM Chapter 20 will be applied to the facility defined by this section. It was determined in sub-problem 1b that this facility has characteristics that could normally be associated with both Class I and Class II two-lane highways. Therefore, the analysis will be repeated for both Class I and Class II facilities, and the results will be compared. The results will also be compared with those of the planning level analysis performed in sub-problem 2b.

What are the differences in analyses for Class I and II facilities? We will begin with a discussion of the differences in the LOS estimation procedures for Class I and II facilities.

As we pointed out in sub-problem 3a, the key performance measures for two-lane highways are the percent time spent following (PTSF) and the average travel speed (ATS). The LOS thresholds for these measures are shown in Exhibit 3-19 for both facility Classes.

On a Class I facility, the more critical of the two measures will determine the LOS. On a Class II facility, only the PTSF is considered, and the LOS thresholds for Class II are shifted upwards by 5 percentage points from Class I to reflect the lower driver expectation on a Class II highway. For example, the threshold for LOS E for Class I facilities is 80% and for Class II facilities it is 85%. One important point is that the performance measures will be computed in exactly the same way for both classes. In other words, the Class that you specify will not affect either the PTSF or the ATS. Only the thresholds will be applied differently.