Guide on The Consistent Application of Traffic Analysis Tools and Methods

CHAPTER 1. INTRODUCTION

The FHWA, in support of the Traffic Analysis and Simulation PFS, initiated this study to identify and address consistency in the selection and use of traffic analysis tools. This report offers recommendations on the management, planning, and conduct of traffic analysis that will promote greater traffic analysis tool consistency over the typical project development life cycle. It is directed toward professionals operating in State departments of transportation and other agencies responsible for transportation project development and delivery.

PURPOSE

The purpose of this guidebook is to provide technical advice on the selection and use of traffic analysis tools and other methods in a manner that promotes consistency over the course of the project development life cycle. This guidebook is designed to do the following:

• Offer advice on setting up consistent study assumptions and parameters and on selecting MOEs that are as directly comparable as possible.

• Offer advice on how to prepare each type of analysis in a manner that allows the MOEs of different tools to complement one another without confusing and contradictory results.

• Offer advice on the utilization, interpretation, and integration of the range of data and multiple measures produced by multiple traffic analysis tools employed over a project's development life cycle.

• Provide interim direction, drawing upon current and ongoing efforts, until such time as superior application guidance or functionality can be provided by the vendor community or through further research.

• Provide an approach to the development of a study scope in a manner that anticipates the analysis requirements throughout the life cycle of a study. Consideration should be given to the benefits and limitations of conducting larger geographic studies useful for more stages of project analysis versus the agglomeration of smaller, more focused traffic analysis studies into a larger, unified analysis. The guidance offers advice on how to develop studies in a consistent and scalable manner.

TARGET AUDIENCE

The primary audience for this guidance is the technical staff associated with participating State and other government agencies associated with the PFS on Traffic Analysis and Simulation, TPF-5(176).

APPROACH

Development of this guidebook included a preliminary literature review to assess the quality of the guidance currently available on the use of traffic analysis tools to achieve consistent analytical results. An expert panel was recruited to review interim results and provide guidance on the technical direction of the effort. A questionnaire was distributed and a series of interviews conducted that culminated in a report on the current state of the practice. Feedback to that report, additional interviews, and literature review were conducted to support identification of key consistency issues and to support the development of this document.

Terminology and processes contained in this guidebook are a composite of the experiences of and approaches used by transportation agencies across the country for instructive and consistency purposes. When using this guidance, individual agencies will need to consider how their own terminology, processes, and procedures correspond to those contained in this document.

PROBLEM STATEMENT

Initial interviews with State transportation staff revealed that, though reference documents are generally available for most analysis tools, it is often difficult to incorporate the documents' guidance into actual practice. This is often because of staff, budget, and resource limitations. However, a significant hindrance is that each available reference is focused on a specific analysis tool and not on how the tool fits into the complete project development life cycle.

Additional interviews with senior-level analysts and practitioners revealed that managers face many challenges in identifying and assembling the appropriate level of effort, staff, and support needed to employ the variety of traffic analysis tools required to meet traffic analysis goals.

For most State transportation agencies, issues with tool use inconsistency do not reflect a need for additional tool references. A central theme in the course of this study was that despite the existence of tool-specific references, the guidance and recommendations contained in those references have not always been adequately implemented for various reasons, including the disjoint nature of the guidance. Guidance is given on how to use the specific tool but not on how the use of the tool fits into an overall traffic analysis process.

This report attempts to bridge the gaps between available tool-specific references by providing an overall management approach to the employment of traffic analysis tools over the life cycle of project development. This report is not focused on telling analysts how to use specific traffic analysis tools because that information is already available from references such as the FHWA Traffic Analysis Tools Program.⁽¹⁾ Instead, this report recommends steps that technical analysts and project development managers can take to improve the consistency and effectiveness of their traffic analyses over the course of the project development life cycle.