U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
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| Publication Number: FHWA-HRT-15-027 Date: November 2015 |
Publication Number: FHWA-HRT-15-027 Date: November 2015 |
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In the past, communicating messages legibly on electronic changeable message highway signs (CMS) was limited by older CMS technology to textual information, using just a few fonts. Today, CMS technology has advanced to the point where messages can display graphical information, including exact replicas of standard highway signs, and Federal Highway Administration fonts. Although what can be displayed on CMSs intended for highway applications is limited, the technology is capable of producing full color, animation, and video, and can display these images in bright daylight. This project examined the distraction potential of information sources in the right-of-way, with a focus on the latest generation of CMS technology that is capable of displaying any type of message—large or small letters, graphics, and symbols. In one of the experiments, drivers did not look at the salient images (faces on brightly colored backgrounds) more often or longer than they looked at travel-time messages.
In addition to CMSs, the project evaluated the distraction potential of increasing the number of supplemental guide signs associated with a single interchange and potential information overload effects on drivers, from the frequency and spacing of guide signs. The results of that study supported retaining current Manual of Uniform Traffic Control Devices for Streets and Highways standards and recommendations for guide signs and suggested further research on the design of specific-service logo signs. The research should be useful to engineers interested in standards for highway signing, to Transportation Management Center operators interested in conveying messages that complement driver behavior and to researchers interested in assessing driver visual attention.
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.
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. FHWA-HRT-15-027 |
2. Government Accession No. | 3 Recipient's Catalog No. | ||
4. Title and Subtitle Information as a Source of Distraction |
5. Report Date November 2015 |
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6. Performing Organization Code |
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7. Author(s) Vaughan W. Inman, Mary Ann Bertola, Brian H. Philips |
8. Performing Organization Report No.
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9. Performing Organization Name and Address Leidos |
10. Work Unit No. (TRAIS) | |||
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11. Contract or Grant No. DTFH61-08-C-00006 |
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12. Sponsoring Agency Name and Address Manual of Uniform Traffic Control Devices Team |
13. Type of Report and Period Covered Final Report. 7/15/2011–9/30/2013 |
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14. Sponsoring Agency Code HOTO-1 |
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15. Supplementary Notes The FHWA Contracting Officer's Technical Representative was David Yang. |
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16. Abstract The overall goal of the Information as a Source of Distraction project was to further the scientific basis for decisions about the types of information that can be displayed within the right-of-way without adversely affecting drivers’ attention to their primary task—safe driving. There were two focus areas: electronic changeable message highway signs (CMS) and guide signs. Six studies were conducted. The first study examined the perceived similarity between messages on a full-color, full-matrix, light-emitting diode CMS display with 0.79-inch (20‑mm) pixel pitch and the same messages on a liquid crystal display. The purpose of that study was to derive requirements for laboratory and driving simulation studies of CMS messaging. The second study examined the legibility distance for text message on the CMS display used in the first study. It was determined that, assuming 20/40 vision, legibility distance could be estimated using a letter height of 1 inch (2.54 cm) per 20 ft (6.1 m) of viewing distance. In the third study, drivers read the CMS display as they approached it on a closed course that required them to simultaneously navigate a curved path. The effects of CMS message properties such as flashing, phasing, abbreviations, and use of symbols versus text were examined. The fourth and fifth studies simulated overhead CMS messages on a freeway on which there was a CMS every 0.5 mi (0.8 km). By displaying highly salient images (faces on brightly colored backgrounds) that changed every 3 s, an attempt was made to distract drivers. Drivers did not look at the salient images more often or longer than they looked at travel-time messages. When headways were short, the salient signs had a 0.2 probability of receiving a brief look. None of the signs caused drivers to miss safety-critical messages encountered later in the drive. None of the signs caused drivers to fail to detect a roadway hazard (spilled logs). The final study examined the effects of the frequency and spacing of guide signs on navigation performance and eye-glance behavior. That study supported retaining current Manual of Uniform Traffic Control Devices for Streets and Highways standards and recommendations for guide signs and suggested further research on the design of specific service logo signs. |
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| 17. Key Words
Distraction, Changeable message sign, CMS, Supplemental guide sign, Specific service sign, Sign spacing, Sign frequency, Sign content |
18. Distribution Statement
No restrictions. This document is available through the National Technical Information Service, |
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19. Security Classification Unclassified |
20. Security Classification Unclassified |
21. No. of Pages 137 |
22. Price
N/A |
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| Form DOT F 1700.7 (8-72) | Reproduction of completed page authorized |
SI* (Modern Metric) Conversion Factors
Chapter 1. Introduction to the Information as a Source of Distraction Project
Chapter 2. Laboratory Evaluation of CMS
Chapter 6. The Effect of CMS Information on Detection of Safety-Critical Events in the Roadway
Chapter 7. The Effect of Frequency and Spacing of Guide Signs on Driver Behavior
| AASHTO | American Association of State Highway Transportation Officials |
| CIE | Commission Internationale de l'Eclairage (International Commission on Illumination |
| CMS | Electronic Changeable Message Highway Sign |
| FHWA | Federal Highway Administration |
| GEE | Generalize Estimating Equation |
| ITS | Intelligent Transportation System |
| LCD | Liquid Crystal Display |
| LED | Light-Emitting Diode |
| M | Mean |
| MUTCD | Manual on Uniform Traffic Control Devices for Streets and Highways |
| NCHRP | National Cooperative Highway Research Program |
| NEMA | National Electrical Manufacturers Association |
| NTCIP | National Transportation Communications for Intelligent Transportation System Protocol |
| PRC | Percent of Road Center |
| RGB | Red, Blue, Green |
| ROI | Region of Interest |
| SE | Standard Error of the Mean |
| SDG | Standard Deviation of Gaze Angle |
| TCD | Traffic Control Device |
