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Publication Number:  FHWA-HRT-13-082    Date:  July 2013
Publication Number: FHWA-HRT-13-082
Date: July 2013


Saxton Transportation Operations Laboratory

Traffic Bottlenecks - Identification and Diagnosis, Countermeasure Prioritization, and Innovative Solutions to Local/Systemic Problems

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Often entire regions are overwhelmed by increasing traffic demand and limited ability to implement expensive systemic improvements to mitigate congestion. In 2010 alone, the estimated cost of congestion was $101 billion.1

In recent years, the Federal Highway Administration (FHWA) has led research efforts and produced publications related to congestion identification, diagnosis, and mitigation. Through these efforts, FHWA has found that a large percentage of traffic congestion results from recurring causes, including bottlenecks. Due to rising costs related to congestion, it is important to diagnose and identify cost-effective bottleneck solutions; however, the current body of knowledge surrounding traffic congestion is dated and in need of updating and revision. Some recurring congestion occurs at specific locations on the highway system, where periodic volume surges coupled with roadway geometrics overwhelm the physical capacity of roadway segments, creating traffic bottlenecks. Transportation agencies have observed that traffic bottlenecks can be alleviated using low-cost and cost-effective solutions, resulting in a better benefit-cost ratio than more expensive infrastructure investments. Therefore, research and analysis efforts toward developing and evaluating low-cost and cost-effective traffic bottleneck solutions are promising.

The existing research does not clearly separate causes of recurring congestion into categories needed to identify causalities. This project aims to provide guidance on the characteristics of congestion and bottlenecks that occur on a facility level; to investigate existing innovative and cost-effective solutions to bottlenecks; and to disseminate information to researchers and practitioners for practical use in combating traffic congestion and bottlenecks.


Diagram depicts the process to be undertaken in FHWA's project to diagnose countermeasure prioritization and identify innovative solutions to local/systemic bottlenecks. The process begins with defining congestion, including external influences, speed, and volumes. It then proceeds to developing a prototype application for agencies to use in identifying  congestion. The third step is classifying congestions. This step is represented by a pie wheel comprising the causes of nonrecurrent congestion, including traffic incidents, work zones, inclement weather, signal timing, and special events/other. A note indicates these events influence demand and capacity. Each of these causes is broken down into recurring localized bottlenecks and recurring systemic congestion, both of which may contain elements of nonrecurring localized congestion and nonrecurring system congestion. For non-recurring localized and systematic congestion, demand is greater than capacity with a combination of traffic volumes and composition as the sole cause and no other influencing causes.  The fourth step in the process is to prioritize the bottlenecks needing treatment and, finally, the fifth step is to diagnose and develop innovative and cost-effective solutions for traffic bottlenecks.

Project Objectives

A congested highway at nighttime with traffic entering from onramps, adding to the backup.

A time-elapsed photo of a highway at night with headlights and taillights streaming into the distance as cars travel toward and away from the camera.

Project Overview by Task

Engagement with Stakeholders

Inform – Provide effective marketing and outreach material outlining ongoing congestion and bottleneck research.

Educate – Provide new and existing information on congestion and bottlenecks to State and local agencies and transportation professionals.

Interact – Generate effective outreach efforts to allow practitioners and researchers opportunities to interact and discuss problems and solutions surrounding congestion and bottelenecks.

Influence – Create opportunities for diverse groups to influence development of new and innovative solutions to reduce congestion and bottlenecks.

Collaborate – Provide a platform for collaboration among various groups with an interest in reducing congestion and bottlenecks through cost-effective solutions.

Partner – Work with various agencies and individuals to identify diverse solutions to congestion and bottlenecks.

Aerial photo of a very congested multi-lane toll plaza.

For more information on the project, please contact:

Joe Bared, FHWA

Randy VanGorder, FHWA

1 Schrank, D., T. Lomax, and B. Eisele, 2011 Urban Mobility Report. Texas
Transportation Institute, September 2011. Available at http://mobility.tamu.edu
2 Influencing demand and capacity
3 Combination of traffic volumes and composition as sole cause, no other influencing causes