Use text-only messages instead of graphic-aided messages on dynamic message signs during traffic slow-downs.

Findings from a traffic analysis, driver surveys, and driving simulator experiment used to evaluate the impacts of dynamic message signs (DMS).

Statewide; Rhode Island; United States

Background (Show)

Lesson Learned

The study took a three pronged approach:
  • Traffic data analysis: traffic data, including volume and speeds, were collected near DMSs in Rhode Island for a two week period. The study compared "pre-display" and "first 30-min" traffic conditions (initiating stage analysis) and "last 30-min" and "post-display" traffic conditions (ending stage analysis).
  • Driver questionnaire: a 24 multiple-choice question survey collecting drivers' opinions on slow-downs and DMS use. Surveys were administered at multiple locations in Rhode Island to obtain a representative sample of the driving population, 150 drivers participated.
  • Driving simulator experiment: video-based driving simulation developed and conducted to evaluate various DMS message designs in a simulated driving environment. Two main factors, message category and message type, were considered in a factorial experiment with three repetitions. Message categories were: danger warning, informative, and regulatory. Message types were: graphic-aided message with full text (GFT), graphic-aided message with partial text (GPT), and text-only message (T). Each message category was included with each of the message types, yielding nine test messages. A few practice trials were given to ensure participant readiness prior to the actual simulation. Thirty-six (36) drivers participated. Participants sat in a fix-base vehicle and were asked to respond by pressing one of four buttons mounted on the steering wheel once they comprehended the messages.
Lessons Learned
  • Traffic data analysis. Decrease in both speeds and headway distances in the "initiating stage analysis" and increase in both speeds and headway distances in the "ending stage analysis" provided evidence of impacts of active DMSs on highway traffic.
  • Driver questionnaire. Most drivers indicated they reduced speed when approaching an active DMS. Lengthy, complex, and abbreviated messages could cause drivers to slow down. Drivers preferred text-only messages over graphic-aided messages and single frame over two-frame messages when displaying the same content. Two-frame messages with more information were preferred over single-frame messages with less information and abbreviations.
  • Driving simulator experiment. GPT messages had similar response time when compared with T messages but shorter response time compared to GFT messages. Overall, young participants (age 18-40) responded the fastest. Female participants responded faster than males except for the oldest age group. Participants responded faster to danger warning messages than other message categories.
Graphics may not be well accepted by drivers for use in DMS messages as indicated by the survey, yet graphic-aided messages with partial text showed promising results by producing quick response and higher response accuracy in the driving simulation experiment.

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Assessing and Mitigating the Impacts of Dynamic Message Signs on Highway Traffic

Author: Song, Miao; Jyh-Hone Wang; Sam Cheung; and Merve Keceli

Published By: Scientific Research Journal Ltd.

Source Date: 02/29/2016

URL: http://www.ijtte.com/uploads/2016-03-08/935be804-af35-8184IJTTE_Vol%206(1)_1.pdf

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Janet Fraser


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Rhode Island


United States

Systems Engineering

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System Requirements


Dynamic Message Signs, CMS, VMS, Changeable Message Signs, Variable Message Signs, construction warning signs, Portable Dynamic Message Signs, portable CMS, portable VMS, portable Changeable Message Signs, portable Variable Message Signs, Temporary Dynamic Message Signs, Temporary CMS, Temporary VMS, Temporary Changeable Message Signs, Temporary Variable Message Signs

Lesson ID: 2017-00768