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Coordinating, Developing, and Delivering Highway Transportation Innovations

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Publication Number:  FHWA-HRT-20-008    Date:  May 2020
Publication Number: FHWA-HRT-20-008
Date: May 2020


Alternative Designs to Alleviate Freeway Bottlenecks at Merging, Diverging, and Weaving Areas

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Merging, diverging, and weaving areas are major bottleneck locations on uninterrupted flow facilities and are a significant source of recurring congestion. This report summarizes the development of five alternative designs for application at freeway merging, diverging, and weaving areas: split merge points, managed lanes on the right-hand side, mainline metering, coordinated ramp metering, and speed optimization via traffic calming devices. This report also includes simulations of the innovative treatments to evaluate the benefits of the designs. This report will be of interest to State and local departments of transportation who are interested in exploring innovative methods to more effectively manage their facilities.

Brian P. Cronin, P.E.
Director, Office of Safety and Operations
Research and Development


This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No.


2. Government Accession No. 3 Recipient's Catalog No.
4. Title and Subtitle

Alternative Designs to Alleviate Freeway Bottlenecks at Merging, Diverging, and Weaving Areas

5. Report Date

May 2020

6. Performing Organization Code
7. Author(s)

David K. Hale (ORCID: 0000-0001-5486-9367), Jiaqi Ma (ORCID: 0000-0002-8184-5157), Amir Ghiasi (ORCID: 0000-0002-0986-9840), Pascal Volet (ORCID: 0000-0002-1753-0935), Burak Cesme (ORCID: 0000-0002-1265-981X), Alexandra Kondyli (ORCID: 0000-0002-3462-0000), Bastian Schroeder (ORCID: 0000-0001-8916-421X), Sonika Sethi (ORCID: 0000-0002-5236-0003), Laura Torres (ORCID: 0000-0001-8250-0436), and Francois Belisle (ORCID: 0000-0003-1592-3986)

8. Performing Organization Report No.

9. Performing Organization Name and Address

Leidos, Inc.
11251 Roger Bacon Drive
Reston, VA 20190-5201

10. Work Unit No.
11. Contract or Grant No.


12. Sponsoring Agency Name and Address

U.S. Department of Transportation
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report; July 2017–September 2018

14. Sponsoring Agency Code


15. Supplementary Notes

The Contracting Officer's Representative was Joe Bared (HRDO-20).

16. Abstract

Alternative intersections and interchanges brought major benefits to the United States during the 2008–2018 time period. Given the positive impacts, it stands to reason that similar breakthroughs might be possible at freeway merge and diverge locations. This report describes the outcomes of a project that examined this possibility. The primary tool of evaluation was sensitivity analysis via microscopic traffic simulation, also known as microsimulation. The split merge design, and the positioning of managed lanes on the right side of the freeway, are two unrelated designs that showed excellent promise (in terms of benefit—cost ratio). Coordinated ramp metering did not show significant additional benefits beyond conventional asservissement lin’eaire d'entr’ee autorouti‘ere, also known as ALINEA, metering. Speed optimization showed excellent benefits but only during narrow ranges of traffic congestion. Mainline metering also showed reasonably good benefits but could be challenging to implement. It is conceivable that speed optimization and mainline metering could produce more favorable benefit—cost ratios if they could be implemented via connected and automated vehicle (CAV) technologies. However, the split merge and right-side managed lane designs produced excellent benefits without the need for CAV technologies.

17. Key Words

Split merge, managed lanes, mainline metering, coordinated ramp metering, speed optimization, freeway merge

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.

19. Security Classification
(of this report)


20. Security Classification
(of this page)


21. No. of Pages


22. Price


Form DOT F 1700.7 (8-72) Reproduction of completed page authorized



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