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Publication Number: FHWA-HRT-13-048
Date: October 2013

 

Driver Expectations When Navigating Complex Interchanges

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FOREWORD

Interchange navigation presents a range of challenges that are different from those associated with driving on continuous roads. For example, interchanges force drivers to make time-sensitive task demands (i.e., forced-paced tasks). More specifically, drivers at unfamiliar interchanges must read the available signage, observe pavement markings, and determine a path through the interchange before they reach the gore point. Additionally, driver errors at interchanges are often more difficult to correct since drivers may transfer to a grade-separated freeway, highway, or roadway that provides limited access points to return to the original roadway. Clear navigation signage is needed to guide drivers and reduce errors.

Although there has been previous research performed on signage in general, research specifically on interchange signage has been limited. There is little consensus on a best way to design signs for interchanges, and, in general, the current data on sign design is incomplete. The objective of this project was to begin addressing these information needs. This project yielded several overall conclusions related to driver expectations at complex interchanges. Namely, most drivers have problems at complex unfamiliar interchanges and feel stressed when they are surprised, are required to perform multiple lane changes in a short distance, or do not receive the information they expect. Several recommendations for sign designs are offered to help address these conditions. This report will be useful to traffic-safety researchers and traffic engineers responsible for highway design and public safety.

Monique R. Evans
Director, Office of Safety
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

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

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Technical Report Documentation Page

1. Report No.

FHWA-HRT-13-048

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

Driver Expectations When Navigating Complex Interchanges

5. Report Date

October 2013

6. Performing Organization Code
7. Author(s)

Christian M. Richard and Monica G. Lichty

8. Performing Organization Report No.

 

9. Performing Organization Name and Address

Battelle Seattle Research Center
1100 Dexter Avenue North, Suite 400
Seattle, WA 98109

10. Work Unit No. (TRAIS)

11. Contract or Grant No.
12. Sponsoring Agency Name and Address

Office of Safety Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report

14. Sponsoring Agency Code

 

15. Supplementary Notes

The Contracting Officer's Technical Representative (COTR) was Jim Shurbutt, HRDS-30.

16. Abstract

The purpose of this project was to develop a method for determining driver expectations at interchanges and to use that method to determine how these expectations affect driver behavior at interchanges that vary in level of complexity, including provision of initial recommendations for navigation signage to aid complex interchange design. Interchange navigation presents a range of challenges that are different from those associated with driving on continuous roads, and driver errors at interchanges are often more difficult to correct since drivers transfer to a grade-separated freeway, highway, or roadway, which provides limited access points for their return to the original roadway. Clear navigation signage is needed to guide drivers and minimize errors. Although there has been previous research performed on signage in general, research specifically on driver expectations and interchange signage has been limited. Moreover, there is little consensus on a single best way to design signs for interchanges, and available data present an incomplete picture of guidance relevant to sign design.

 

This project involved multiple tasks to study driver expectations, including: (1) a literature review of prior work on driver navigation problems and driver expectations at interchanges, (2) a series of focus groups to collect qualitative information about driver expectations, (3) a task analysis of different interchange navigation scenarios, and (4) an experimental study to collect data on driver performance given various complex interchange signage alternatives.

 

This project yielded several overall conclusions related to driver expectations at interchanges. The focus groups indicated that most drivers have problems at complex, unfamiliar interchanges, and they become stressed when they do not receive the information they expect, if they are surprised, or required to execute multiple lane changes in a short distance. The task analysis indicated that multiple concurrent driving tasks may be common in complex interchanges, and could lead to higher workload. Finally, the empirical data collection activities showed, among other findings, that perceptual factors associated with the spatial layout of signs have a significant impact on driver interpretation of guidance information. The problems that drivers experience, and their responses to those challenges potentially have implications for safety and capacity at complex interchanges.

17. Key Words

Complex Interchanges, Interchanges, Signage, Driver Behavior

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)

Unclassified

20. Security Classification
(of this page)

Unclassified

21. No. of Pages

203

22. Price
Form DOT F 1700.7 Reproduction of completed page authorized

 

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