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Subproblem 3a - Page 5 of 5

ID# C303A05

Sub-problem 3a: Analysis of the North Section of Krome Avenue (Class I Two-lane Highway Facility)

The question of base free flow speed deserves further discussion. The service volume tables deal in 5 mph increments of free flow speed. The operational method requires a specified base free flow speed, which is adjusted to reflect the effects of the specified shoulder width and the number of access points per mile in computing the actual free flow speed. In the course of the computations, the actual free flow speed was adjusted downwards in this case by 1.5 mph. So, to promote a fair comparison, the base free flow speed was specified as 56.5 mph, to produce the same free flow speed of 55 mph that was used by the service volume tables. This modification to the base free would not normally be recommended as a sound analytical practice. It was applied in this sub-problem to facilitate comparison between the planning and operational level procedures.

The HCM Chapter 20 procedure has given an overall level of service for this facility based on the performance measures for two-lane roadways. This procedure does not recognize any intersection-related problems. Therefore, a complete assessment of the facility requires a check of all intersections to ensure that problems are not being overlooked. The proper procedures to apply to intersections are found in HCM Chapter 16 (signalized) and HCM Chapter 17 (unsignalized). The details of the intersection analyses will not be presented here; however, it was found that two intersections experienced problems that will require further attention.


The intersection with Okeechobee Rd operates under two-way stop control (TWSC). This is a T intersection in which Krome Avenue is stopped at its northern terminus. The northbound approach here is oversaturated, and mitigation measures will be required. The alternative measures will be discussed in Problem 4.


The southern boundary of this section includes conditions that warrant further consideration. In this case, the cross street movements at Kendall Road are oversaturated. Mitigation measures will be discussed in Problem 5.

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