No abstract

Summary: A human factors study was carried out to help enhance ways to communicate with highway motorists through dynamic message signs (DMS). Overhead mounted DMSs have been increasingly used by highway authorities in the United States to present real-time traffic information and travel advice to motorists. It is critical to post sign messages that can be quickly and clearly understood by motorists, especially in high-volume traffic and construction/repair zones. Properly worded and formatted sign messages could spell the difference between comprehension and confusion. Message display factors investigated in the study include display effects, color schemes, wording, and formats. Two approaches were employed in this study. First, a questionnaire survey was developed to collect motorists' preferences regarding various message display factors. Second, a series of lab driving simulation experiments were set up to assess the effects of these factors and their interactions on motorists' comprehension of DMS messages. Study results suggested that static, one-framed messages with more specific wording and no abbreviations were preferred. Amber or green or a green-amber combination were the most favored colors. Younger subjects took less response time to the DMS stimuli with higher accuracy than older subjects. There were no significant gender differences.

No abstract

Abstract:In an increasingly mobile era, the wide availability of technology for texting and the prevalence of hands-free form have introduced a new safety concern for drivers. To assess this concern, a questionnaire was first deployed online to gain an understanding of drivers' text driving experiences as well as their demographic information. The results from 232 people revealed that the majority of drivers are aware of the associated risks with texting while driving. However, more than one-fourth of them still frequently send or read text messages while driving. In addition to the questionnaire, through the use of a virtual-reality driving simulator, this study examined drivers' driving performance while they were engaged in some forms of text driving under different challenging traffic conditions. Through a blocked factorial experiment, drivers would either read a text message or respond to it with two levels of text complexity while using either hand-held or hands-free texting method. Their driving performance was assessed based on the number of driving violations observed in each scenario. Conclusions regarding the impacts of different forms of texting, text complexity, and response mode on drivers driving performance were drawn.

A study on the message display formats of portable variable message signs (VMSs) is presented. Through a series of laboratory driving simulation experiments, the influences of the interaction between display format and number of message lines and driving lanes were investigated. In the simulation, digitally created VMS stimuli were inserted into a driver's-view driving video, and the video was projected onto a screen in front of a stationary vehicle. Eighteen subjects from three age groups with balanced gender participated in the experiments. Each subject, sitting in the driver's seat of the vehicle, was required to make proper responses signaling comprehension of the VMS stimuli. Subjects’ responses and accuracy were recorded in a database. On the basis of the statistical analysis of the collected data, it was found that discretely displayed messages took less response time than sequentially displayed messages. Singleline messages were better than multiple-line messages. Motorists could better view portable VMSs when they were driving in the outer lane. It was also found that older drivers exhibited slower response and less accuracy than younger drivers; women drivers exhibited slower response but higher accuracy than men drivers.