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Coordinating, Developing, and Delivering Highway Transportation Innovations

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Publication Number:  FHWA-HRT-17-048    Date:  May 2018
Publication Number: FHWA-HRT-17-048
Date: May 2018


Enhancing Safety and Operations at Complex Interchanges With Improved Signing, Markings, and Integrated Geometry

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The National Highway System has experienced rapid growth in demand that has far outpaced the increase in new capacity. Roadway designers are turning toward additional lanes, preferential lanes and ramps, and multilane exits in their interchange designs to address the continued mobility demands. While these mobility and capacity enhancements address the challenge of increased demand, they also complicate the design and operation of interchanges.

Drivers approaching these complex interchanges are required to perform several navigation tasks that are often short in both distance and time. The purpose of this study was to develop recommendations for signing, delineation, and geometric design that will reduce workloads at critical points approaching complex interchanges. In doing so, this project identified many attributes that contribute to complexity; evaluated multiple interchanges across the United States for their design, signing, and marking practices; conducted a series of driving simulator studies; and observed and analyzed video investigating real-world driving behaviors at complex interchanges.

Each key finding and recommendation is provided in the report, along with examples that explain the involved principles and suggested guidelines for implementation. This report should be useful to transportation professionals, State transportation departments, and researchers interested in developing complex interchange designs that consider driver behavior more effectively.

Monique R. Evans, P.E., CPM
Director, Office of Safety
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.

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Technical Report Documentation Page
1. Report No.
2. Government Accession No. 3. Recipient’s Catalog No.
4. Title and Subtitle
Enhancing Safety and Operations at Complex Interchanges with Improved Signing, Markings, and Integrated Geometry
5. Report Date
May 2018
6. Performing Organization Code
7. Author(s)
Steve Jackson, Bryan Katz, Scott Kuznicki, Erin Kissner, Nicholas Kehoe, and Sheryl Miller
8. Performing Organization Report No.
9. Performing Organization Name and Address
Toxcel, LLC
7140 Heritage Village Plaza
Gainesville, VA 20155

Leidos, Inc.
11951 Freedom Drive
Reston, VA 20190
10. Work Unit No. (TRAIS)
11. Contract or Grant No.
12. Sponsoring Agency Name and Address
Office of Safety
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296
13. Type of Report and Period Covered
Final Report; 2014–2016
14. Sponsoring Agency Code
15. Supplementary Notes
The Contracting Officer’s Representative was Jim Shurbutt (HRTM-30), and the Government’s Task Manager was William Perez (Leidos).
16. Abstract
The purpose of this study was to develop recommendations for signing, delineation, and geometric design that will reduce workloads at critical points approaching interchanges that exhibit a high degree of complexity. In the development of these recommendations, the following activities were completed: identification of attributes influencing interchange complexity; evaluation of current geometric design, signing, and marking practices; a simulator study investigating driver behavior at different interchange layouts; and a field study investigating real-world driver behavior at complex interchanges.
This report details the process and outcomes of these activities to develop key findings with regard to traffic control devices, pavement markings, and geometric design being implemented across the country. Six categories of recommendations (“treatments”) were identified and discussed. Each treatment is the result of understanding the interrelationships of various attributes within each research topic and the application of those relationships to practice outcomes. The report describes each treatment with examples of undesirable practices as well as anticipated and observed outcomes, provides existing design guidelines with a general perspective on implementations in multiple jurisdictions, outlines the primary principles of the concept, provides application examples, provides specific recommendations to address undesirable practices, and summarizes the breadth and depth of implementation options.
17. Key Words
Traffic control devices, pavement marking, geometric design, human factors, simulator study, field study, recommendations, best practices
18. Distribution Statement
No restrictions. This document is available through the National Technical Information Service, Springfield, VA 22161.
19. Security Classif. (of this report)
20. Security Classif. (of this page)
21. No. of Pages
22. Price

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

SI* (Modern Metric) Conversion Factors

Table of Contents

List of Figures

List of Tables

List of Acronyms and Abbreviations

AASHTO American Association of State Highway and Transportation Officials
APL arrow-per-lane
C/D collector–distributor
CMV commercial motor vehicle
CSV comma-separated values
DAQ data acquisition
DP1 first decision point
DP2 second decision point
FHWA Federal Highway Administration
GDOT Georgia Department of Transportation
GPS Global Positioning System
HO/T high-occupancy vehicle and tolling
HOV high-occupancy vehicle
HFs human factors
I- Interstate
ITE Institute of Transportation Engineers
LSD lane selection distance
MHFL Mobile Human Factors Laboratory
MnDOT Minnesota Department of Transportation
MUTCD Manual on Uniform Traffic Control Devices
RRPM raised reflective pavement marker
SHS Standard Highway Signs Catalog
SR state route
SSQ Simulator Sickness Questionnaire
TCD traffic control device
TH 62 State Trunk Highway 62
TMC traffic-management center
UAV unmanned aerial vehicle
ULC unnecessary lane change
US United States Route
WSDOT Washington State Department of Transportation
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000
Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101