Visual Perception and Understanding of Variable Message Signs: The Influence of the Drivers’ Age and Message Layout

Gianfranco Fancello,Claudia Pinna,Patrizia Serra

doi:10.3390/safety7030060

Gianfranco Fancello, Claudia Pinna + Show 1 more

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https://doi.org/10.3390/safety7030060

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Abstract

Variable message signs (VMS) are used to display messages providing up-to-date traffic-relevant information so that drivers can safely adapt their behavior in real time. The information reported in a VMS should be brief but comprehensive to minimize perception time. The latter can be influenced by the way the message is displayed. This study investigates how the different ways of displaying the same message can influence reading time and the information perception process at different driving speeds. Specifically, the following message characteristics are investigated: (i) use of uppercase and lowercase letters; (ii) use of familiar pictograms; and (iii) use of less familiar pictograms. Furthermore, as perception time typically changes with ageing, drivers belonging to three different age classes are tested. The experimentation was performed by simulating a vehicle passing along a straight road upon which a VMS displaying different messages was placed. Experimentation results are analyzed using the Kruskal–Wallis test, Friedman rank-sum test and Welch one-way ANOVA, showing that: (i) the use of uppercase or lowercase does not seem to significantly affect reading times; (ii) the use of pictograms that are not very familiar to habitual road-users can be counterproductive for the perception process; (iii) elderly drivers always have greater difficulty in perceiving the message than young or middle-aged drivers. The findings of this study can be of help for traffic authorities to design the most suitable structure for a VMS so that its information can be unequivocally and immediately conveyed to drivers.

Highlights

The last two decades have seen the increased use on roads of intelligent transport systems designed to facilitate safe driving while reducing driver fatigue and distraction
This study has investigated, by means of an objective method based on a simulation experiment, the extent to which some features of the messages displayed in variable message signs (VMS) may influence reading time and understanding rates and whether and how these latter factors can be affected by the driver’s age and driving speed
Drivers showed a longer reading time and greater difficulty in correctly perceiving the message than young and middle-aged drivers. This result is not surprising, as ageing typically causes deterioration of vision and a reduction in visual acuity, reducing the ability to capture the fine details of a visual stimulus, such as the text displayed in a VMS

Summary

Introduction

The last two decades have seen the increased use on roads of intelligent transport systems designed to facilitate safe driving while reducing driver fatigue and distraction. These include variable message signs (VMS), which provide drivers with information (e.g., on accidents, route choice and congestion) in real time so that they can adapt their behavior . Compared to fixed road signs, VMS have better potential to provide road users with instantly updated messages on road and traffic conditions. Messages should be short yet comprehensive, and reading time needs to be reduced to a minimum. Reading time can be influenced by both the characteristics of the message (color, length, number of rows, number and size of characters, images, abbreviations, etc.) and external factors, such as panel location and driver’s characteristics [3,4]

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