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HCMAG -- Case Study 2 -- Route 146 Corridor

ID# C2OV001


Printable VersionOverview, Introduction, and Getting Started Printable Version

This case study is about a Traffic Impact Assessment for a proposed site development in Clifton Park, New York (see Exhibit 2-1). The large parcel of land in question is south of where Maxwell Drive intersects with Clifton Park Boulevard (State Route 146). Like most impact assessments, the main question is this: in the horizon year for the analysis, what geometric improvements will be required to mitigate the impacts of the site development in conjunction with normal traffic growth?

The Town of Clifton Park and New York State Department of Transportation (NYSDOT) both have roles to play in the decision-making. So do Saratoga County, the town’s citizens, the nearby land owners, and the developer. There are issues about how many intersections should be studied, what time periods should be examined, what goals and objectives should be used, and what performance measures should be employed.

To address these issues and others, the case study includes six problems. They range in scope from a single intersection to a sub-area network. Each one illustrates some aspect of the impact assessment. Each one also illustrates how various traffic analysis tools in the Highway Capacity Manual can be applied to assist traffic analysts, engineers, planners, and decision-makers in making sound investment decisions regarding changes to a transportation system.

The problems focus on the chapters of the HCM that deal with interrupted flow facilities, especially signalized intersections, arterials, freeway interchanges, and arterial weaving. After studying this material, you should be able to:


Analyze the operation of signalized intersections, unsignalized intersections, and urban arterials using the HCM.


Understand what input data are required and the assumptions that are commonly made regarding default values for the HCM procedures for these facilities.


Know the appropriate kinds of analysis that should be undertaken for existing facilities as well facilities or conditions in the future, including the scope of the analysis.


Understand the limitations of the HCM procedures and when it is appropriate to use other models or computational tools.

bulletKnow how to reasonably interpret the results from an HCM analysis and how these results can be used to support a particular decision regarding a change to a transportation system.

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