Overview

Printable Overview, Introduction, and Getting Started

Krome Avenue is a 33-mile, north-south route that bypasses Miami, Florida, on the west side. It is essentially a rural route that has very little roadside development. Florida’s Turnpike is about 5 miles to the east, providing several east-west connections to Krome Avenue. Its two-lane configuration has limited capacity compared to other facilities such as freeways and multilane roadways. Most of the route now operates well within its capacity, except that some congestion has been observed at critical locations. This is a region of high population growth that is expected to generate continually increasing traffic volumes. Prompted primarily by safety considerations, the posted speeds have already been reduced below the 55 mph level typically found on open highways.

In this case study, identify the goals, objectives and analysis tools for an investigation of the existing level of service on the entire route. We will then apply the analysis tools to assess the current performance of this route and identify areas that are deficient. Then, applying the same analysis tools, we will investigate some alternatives for mitigating the deficiencies.  

The main purpose of the case study is to illustrate the concepts and practice of applying the transportation analysis tools in general and the Highway Capacity Manual (HCM) in particular. Much of the discussion will be based on a recently completed study of Krome Avenue that had similar goals and objectives. Several problems will be presented to illustrate the application of the tools and the interpretation of the results.  

Krome Avenue is an actual highway and the data used in the problems represent actual field data. In some cases the alternative intersection improvements discussed in this case study were chosen for their illustrative value and do not necessarily reflect the recommendations of the original study.

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Getting Started

Printable Overview, Introduction, and Getting Started

Several issues will be considered as we begin this case study, including the scope of the analysis, the stakeholders and their perspectives, the overall goals for the analyses, the performance measures to be used to quantify results for comparison, the tools to be used in performing the analyses, the data requirements of these tools, and the technical details that arise from using the HCM methods in this case study.

Scope of the Analysis
The intersections along this section of Museum Road provide unique characteristics that lend themselves to a variety of analysis techniques. The Museum Road facility itself presents some special considerations that must be taken into account in all analyses, due principally to the close intersection spacing and the significant amounts of pedestrian, bicycle, and bus activity.

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Getting Started

Stakeholders
There are several stakeholder perspectives involved in the analysis and decisions affecting Museum Road, including:

• University of Florida administration must make critical decisions with regard to any mitigating work to be done as a result of the new parking structure. They have to weigh this situation with a multitude of others from budget and resource perspectives to establish this among their priorities and constraints.

• Pedestrian-bicycle advocates have already succeeded in getting other campus streets closed to vehicular traffic. This group will continue to raise the awareness of the pedestrian and bicyclist to ensure they are considered when making plans and decisions that focus on vehicular efficiency, as well as keeping safety in the forefront of these deliberations.

• Public transit interests in the community are very strong and extend into the bus activity within the campus. Ridership among students and university employees (who ride free) is very high, with many depending on this mode to get them to and from class and work.

• Students and employees as motorists need mobility and access to campus facilities and parking. Although parking is very limited on campus, what is in place is virtually always at capacity, requiring a roadway network to accommodate this (mostly employee) traffic affecting Museum Road.

• Campus police have continuing concerns about enforcement of pedestrian rights and obligations, which include uncontrolled pedestrian activity between intersections, outside of crosswalks, and even against pedestrian control.

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Goals and Objectives
The driving force behind this study is to provide sufficient information, detailed analyses, and quantitative results to those responsible for deciding the best solution to mitigate the impacts of this new parking structure on Museum Road. Developing alternatives analyses using the HCM to compute performance measures such as capacity, delay, queuing effects, etc., will assist them in making decisions on intersection control, signal timing and coordination, lane configuration improvements, and pedestrian, bicycle and transit operations and safety.

We should also point out that the Manual on Uniform Traffic Control Devices (MUTCD) is commonly used to determine if a signal is warranted, and in most jurisdictions is the legal document used to determine many of the characteristics of a design. However, it is also useful to compare the forecasted operations of an intersection under different control scenarios. The Highway Capacity Manual provides the tools for such an operational analysis.

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Performance Measures
The Highway Capacity Manual provides several performance measures for intersections, both signalized and unsignalized. For both types of intersections, the primary measure of effectiveness is control delay. Control delay is directly related to level of service (LOS), a range of levels that categorize performance from the point of view of the driver, or the user of the highway system. Level of service (along with v/c ratio, queue length, and other performance measures) will be used to help determine if the intersection of Museum Road and Reitz Union Drive should be changed from stop sign control to signal control.

Analyses
We must complete several computations to gather the required information on the performance of Museum Road under both stop sign and signal control. For convenience, we've divided the analyses into two problems. We will consider each problem separately. We will also see that each problem consists of several separate computations, using the HCM or other tools, such as macroscopic and microscopic simulation programs.

The following set of case study problems will be analyzed:

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Tools
Most of the computations that we conduct in this case study will be with the Highway Capacity Manual, particularly those chapters that deal with intersection. This includes Chapter 16 (Signalized Intersections), and Chapter 17 (Unsignalized Intersections).

For some parts of the analyses, however, and for certain traffic conditions, we might also consider the use of other tools. There is a variety of software tools available that we could use, including macroscopic flow models that consider the progression of traffic platoons from one intersection to the next, and microscopic traffic models that consider both the movement of individual vehicles along an arterial and the details of actuated traffic controller operations.

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Data
Three kinds of data are generally needed for traffic analysis. Demand or volume information specifies the turning movement flows (usually in vehicles per hour) at each intersection approach. Intersection geometry includes the number and configuration of lanes at an intersection and along an arterial. Control conditions include information about the traffic signal system, including signal timing and phasing data. For this particular case study, pedestrian, bicycle, transit, and intersection spacing and queuing data are also very important.

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Technical Issues
The computational procedures of the Highway Capacity Manual are complex, often including a number of default values or assumptions that need to be understood (and sometimes modified) if the procedures are to be applied correctly to specific problems.

This case study presents, and hopefully clarifies, a number of technical issues that often arise in the application of Chapters 16 and 17 of the HCM. The Exhibit 5-9 lists these issues and identifies which are covered in each of the problems presented as part of this case study.

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