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Subproblem 1b - Page 4 of 5

ID# C301B04

Sub-problem 1b: Determining the Facility Class and Scope of the Analysis

Two-lane Highway Class
Next, we must repeat the process to assign a class or classes to the two-lane highway portion of Krome Avenue. Again we must ask whether this portion is sufficiently homogeneous to be analyzed as a single facility, or should it be broken into multiple facilities with different parameters?

The class structure for two-lane highways differs from that of signalized arterials. There are only two classes for two-lane highways:


Class I: These are two-lane highways on which motorists expect to travel at relatively high speeds. Most two-lane highways in rural areas fall into Class I


Class II: These are two-lane highways on which, because of other considerations, motorists do not necessarily expect to travel at high speeds. One of these considerations could be a posted speed well below the free-flow speed for a typical high speed rural road. Another could be a high percentage of trips that are shorter that typical intercity trips that normally take place on Class I facilities.

The Class II category was created to avoid assigning an unacceptable level of service to a facility whose average speed has fallen below the normal expectation for high speed highways for reasons other than heavy traffic volumes. The HCM does not provide quantitative guidance for distinguishing between the two classes. The determination of the highway class is related more to the general nature of the highway and motorist expectations rather than quantitative field data.

The posted speed on Krome Avenue is less than the default 55 mph for high speed rural highways. The section north of Kendall has a posted speed of 50 mph and the section south of Kendall has a posted speed of 45 mph. Both have very little roadside development, but the section south of Kendall has slightly more development than the section to the north. Because of the lower speed limit and increased development, it might be advisable to consider the south section as a Class II facility. In the absence of quantitative guidelines, we will perform the LOS estimation using both classes for this section.

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