Office of Operations
21st Century Operations Using 21st Century Technologies
Table of Contents

Traffic Analysis Toolbox Volume X:
Localized Bottleneck Congestion Analysis
Focusing on What Analysis Tools Are Available, Necessary and
Productive for Localized Congestion Remediation

1.0 Introduction

A significant portion of the nation's traffic congestion problems can be attributed to recurring congestion at specific locations on roadways - conditions that cause bottlenecks. There is now broad consensus that poorly functioning subordinate sections of a facility - rather than the entire facility being "undersized" - is more often than not the predominant problem. In layman's terms, often only the "misfiring" parts of the facility need attention, rather than the much more costly solution of starting over by replacing it or widening it.

A variety of mitigation techniques can reduce the frequency and impact of localized bottlenecks (further defined in Section 2.0). These techniques can range from the most intense (e.g., microsimulation product applications) to the least intense (e.g., sketch planning) with several iterations of tools in between; e.g., simple data summarizations, the Highway Capacity Manual analysis (HCM), empirical analysis, and deterministic tools.

The crux of this document is to help agencies decide which analysis techniques to apply and how. But how should an agency choose which bottleneck analysis tool to apply? Which tools are correctly aligned with which challenges? How should an agency decide when to use a particular bottleneck analysis tool, and when is microsimulation warranted?

This bottleneck analysis tool selection guide was developed to help transportation agency managers decide which analysis is appropriate; and how to apply it cost-effectively. Thoroughly considering these decision-support tools can assure the most efficient use of agency resources to provide the highest level of service (LOS). This guide consists of the following sections:

  • Section 1.0 - Introduction. How are bottlenecks caused? What should be the role of bottleneck analysis in decision-making? What bottleneck mitigation strategies are available?
  • Section 2.0 - Background and Discussion. This section prompts the reader to define the study area through some main criteria.
  • Section 3.0 - What to Analyze? The next step is to decide what level of analysis is appropriate. The availability of resources guides the formulation of alternatives.
  • Section 4.0 - What Level of Analysis is Warranted? This section guides the selection of the most appropriate class of modeling tool.
  • Section 5.0 - Levels of Analysis. What are the various options available to analyze congestion, and specifically, localized congestion?
  • Appendix A - Tool Selection Worksheet. This reference tool guides transportation professionals to identify the appropriate category of
    modeling tool.

Applying this document and the worksheet will create additional analytical consistency and uniformity across state departments of transportation (DOT), Federal, regional, and local transportation agencies.