Federal Highway Administration Operations Research and Development

Saxton Transportation Operations Laboratory

Highway Capacity Manual (HCM) 

Methodology for Alternative

Intersections / Interchanges

Project Objectives

Over the past decade, the Federal Highway Administration (FHWA) has conducted and 

developed extensive research, workshops, technical briefs, and other outreach materials about 

alternative intersections/interchanges. These research efforts and publications have increased 

interest and rapid adoption of alternative geometric designs across the United States. Of the 

many alternative intersection/interchange designs, stakeholders showed significant interest in 

these four:

• Double Crossover Diamond (DCD) interchange (or Diverging Diamond Interchange (DDI)).

• Displaced Left Turn (DLT) intersection.

• Median U-Turn (MUT) intersection.

• Restricted Crossing U-Turn (RCUT) intersection.

Most existing analysis tools supporting the adoption of alternative intersections/interchanges 

involve the use of complex microscopic simulations that are expensive and time consuming. The 

Highway Capacity Manual (HCM) and the Highway Capacity Software (HCS) are widely used 

analytical tools that assess the quality of service for conventional intersections and interchanges. 

However, they do not assess any of the alternative designs considered in this project.

To support the increased exposure and interest in these designs, FHWA is conducting activities 

to integrate alternative intersection/interchange guidance into the HCM and HCS. This will help 

expand the portfolio of design alternatives contained in the HCM and enable a side-by-side 

assessment of their operations in contrast to traditional designs.

Project Tasks

The project consists 

of seven tasks. Task 1 

includes administrative 

activities throughout 

the duration of the 

project. Task 2 

involves identifying 

knowledge and 

methodology gaps 

in the current 2010 

HCM, formulating an 

analysis framework, 

and identifying 

field data collection 

necessary to 

address knowledge 

and methodology 

gaps. Task 3 will determine the applicability of existing HCM models to the new designs, and 

will decide whether data is on hand, or if field data collection and simulation are needed. In 

Task 4, the project team will reduce and analyze field data collected for development of HCM 

procedures during Task 3 and prepare a report consisting of new or modified HCM procedures 

for each intersection/interchange type. Task 5 will involve updating existing HCS modules to 

incorporate the newly developed methods for alternative intersections/interchanges. Tasks 6 and 

7 will produce outreach videos from simulation and the final project report in the form of draft

HCM chapters for alternative intersections/interchanges.

The new HCM guidance 

and procedures resulting 

from this project will assist 

agencies in evaluating 

capacity and quality of 

service for the design and 

operation of alternative 

intersections/interchanges.

Pooled Fund Study 

Partner States 

Alabama, California, 

Colorado, Florida, 

Missouri, North 

Carolina, Nevada, Ohio, 

Washington, Wisconsin

Exactly

What?

Exactly

What?

Exactly

How?

Task 5: Develop a 

Computational Engine 

Execution Execution Task 4:

 Collect Data

Develop Equations/Procedures

Validate Equations/Procedures

Task 1: Project Management/Coordination

Task 6: Develop Video 

Files/Outreach Material

Task 7: Prepare 

Final Report

Task 2: Review 

Current 

HCM/Propose 

Adaptations to 

HCM Methods

Task 3: 

Develop Data 

Collection/

Analysis Plan
For more information on the project, 

please contact:

Randy VanGorder, FHWA

202-493-3266

randall.vangorder@dot.gov

Joe Bared, FHWA

202-493-3314

joe.bared@dot.gov

QUEUE

LENGTH?

U-turn queue length at U-turn 

crossover for a Restricted Crossing 

U-Turn (RCUT) intersection

Publication No.: FHWA-HRT-13-083

July 2013 HRDO-20/07-13(200)E 

Alternative Intersection/Interchange Designs Studied

To Contribute to the Research Team’s Discussion

Inform – Provide effective marketing and outreach material that outlines progress on HCM 

guidance for alternative designs. 

Educate – Provide working tools to State and local agencies and roadway practitioners for 

use on existing or new alternative design projects.

Interact – Generate effective outreach efforts to allow practitioners and researchers 

opportunities to interact and discuss issues and opportunities surrounding alternative designs.

Influence – Create opportunities for diverse groups to influence development of HCM 

guidance for and field deployments of alternative intersections/interchanges.

Collaborate – Provide a platform for collaboration among various groups with an interest in 

alternative designs.

Partner – Work with various agencies and individuals to enhance the value of HCM tools 

available to support the operations of and analysis needs for alternative designs.

The project team is maintaining an online collaboration tool to facilitate announcements, 

forums, and file sharing with project stakeholders, including the advisory and review groups. 

The research team intends to provide project updates and facilitate feedback in a variety of 

relevant forums.

Right-turning vehicles and rightlane merging with through traffic 

at a DLT intersection

Lane utilization at DCD 

interchange (also known as DDI) 

crossovers

DCD interchange (also known as DDI)

DLT Intersection RCUT Intersection

MUT Intersection