Abstract - Authorities around the globe struggle with the question whether variable message signs (VMSs) should solely be used for traffic management or can also be used to display traffic-irrelevant messages, such as commercial advertisements. The main questions in this matter concern 1) traffic safety and 2) traffic flow management on the long-term, and are addressed here in a literature review, followed by an experiment in a driving simulator. For this, thirty-two participants drove the same VMS-equipped motorway eight times before encountering a critical route instruction on its VMS. During these eight drives, one group of participants became familiarised to the VMS always being blank while for the other group it always displayed an advertisement. Results showed that 1) it is likely that commercial advertisements on VMSs will not distract drivers more than traffic management messages do. 2) Although it appears some drivers were blind for the route instruction, there was no evidence this was triggered by advertisements; compliance with the route instruction was similar in both groups. In conclusion, this study provides evidence that VMSs can be safely used to display non-traffic related messages, such as commercial advertisements, provided ergonomic principles are met and distracting features such as motion are refrained from. IntroductionRoad authority experts have been discussing for years whether to display messages on VMSs when they are not in use for traffic management (for an overview see Mitchell, 2011). The question has recently become even more relevant, as in the upcoming years an increasing amount of roadside information currently mostly presented by collective means will be made available to drivers by individual means in their vehicles (Kroon et al., 2014). Because of this shift in accessibility of traffic-relevant (and -irrelevant) information, road authorities will have to rethink their traffic management strategy in relation to current, costly roadside equipment. For example, the national Dutch road authority has recently decided to reduce the amount of VMSs and cut back the functionality of the remaining VMSs to the core of traffic management (such as the handling of emergency situations). In other words, the remaining VMSs will not be in use for traffic management prolonged periods of time. This raises the question whether these VMSs can be used for non-traffic related purposes in the meantime. To provide some underpinning research for arguments used in the discussion concerning the deployment of commercial advertisements on VMSs this study is carried out. The two main questions in this discussion concern 1) traffic safety (“will commercial advertisements on VMSs distract the driver?”) and 2) traffic flow (“will the VMS still make drivers aware of traffic management information in the long-term, once it also displays commercial advertisements?”). These questions are addressed first in a literature review, followed by an experiment.In the literature a clear distinction is made between commercial advertisements and public service announcements such as road safety slogans. Whereas, as far as known, no research on distracting effects of road safety slogans on VMSs has been carried out, research on commercial roadside advertisements is abundant (SWOV, 2012). Specifically advertisements which involve motion, provoke an emotional reaction, are located in the central visual field and/or resemble traffic-relevant information can result in driver distraction. However, recent studies showed that most roadside advertisements are not visually distracting at all, as long as aforementioned features do not apply (e.g. Decker et al., 2015). The principles which determine whether or not information may distract, do not appear to distinguish between commercial advertisements, traffic information or road safety messages. Previous research seems to indicate that there are yet no reasons to assume that presenting commercial advertisements on VMSs will have more negative effects than displaying road safety slogans or traffic-related information on VMSs. This study is a first attempt to disclose the effects commercial advertisements may have on the perception of traffic-relevant messages for route-familiar drivers.MethodThirty-two experienced drivers participated in the experiment. They were divided in an experimental group who encountered advertisements on an overhead variable message sign (VMS) – which will be referred to as the advertisements group – and a control group for whom the sign was left blank during the same drives. Participants consecutively drove the same road ten times in a driving simulator for them to become familiar with the route. In the ninth drive, all participants encountered a traffic-relevant message on the VMS, informing them they must change their route and take the nearest exit. The last, tenth, drive contained a recollection test. Due to unavailability in the real world, commercial advertisements on VMSs had to be simulated (see Figure 1). Previous studies have shown that visual attention in real-road driving can be comparable to simulated driving (Underwood et al., 2011; Wang et al., 2010). The current study was conducted using the University of Groningen’s STSoftware driving simulator. To detect whether participants had noticed the route instruction on the VMS both their speed and the exit they took were monitored and all comments were logged. Figure 1. Example of an overhead VMS in real-life (left) and in the driving simulator (right), informing drivers they have to deviate from their route. All VMS messages followed the format of a traffic management message in accordance with VMS guidelines of the national Dutch road authority (Rijkswaterstaat, 2012).ResultsThe prerequisite of route-familiarity – necessary to determine longer-term effects, e.g. based on expectations – has been met; drivers from the control group as well as the advertisements group exhibited driving behaviour indicative of habituation.Are drivers aware of the traffic management information presented to them? The results show this question cannot be answered with a simple yes or no as there is some inconsistency in what participants do and what they report. The exit mentioned in the detour message on the VMS was missed by 21.9% of all participants, both of the control group (25%) and the advertisements group (19%). However, some of these participants did pass both the recollection and the recognition test. This suggests they had seen at least part of the route information message – though they failed to act upon it – which was corroborated by comments made by some of them after passing the VMS in drive 9; “did I see that correctly, should I take this exit?” and “the road wasn’t closed at all!”. After completing both the recollection and the recognition task, still 9.4% of all participants persisted in not having seen the crucial route information on the VMS. This included participants of both the control group as well as the advertisements group. Both groups appear to perform similarly in detecting and acting upon the route information.DiscussionThis study leads us to conclude that VMSs can be safely used to display non-traffic related messages, such as commercial advertisements, provided two prerequisites are met. Firstly, advertisements on the VMS should not distract drivers. To our knowledge, research on driver distraction caused by VMSs has predominantly been focussed on ergonomic aspects of messages rather than their semantic content (such as traffic management information versus road safety messages or commercial advertisements). Content-related research on driver distraction for commercial advertisements on billboards, however, is abundant. Based on aforementioned research, we conclude that there are no reasons to assume that displaying commercial advertisements on VMSs will distract drivers any more than messages concerning traffic information or road safety messages; provided they meet ergonomic principles for VMS messages (Dicke & Brookhuis, 2006) and exclude specific characteristics known to distract drivers (Kroon et al., 2014; SWOV, 2012).Secondly, the other prerequisite for non-traffic related messages is that they should not interfere with traffic management. In our study, compliance with the traffic-relevant message was similar for those exposed and those not exposed to commercial advertisements. A study by Jamson and Merat (2007), with public service announcements instead of commercial advertisements, corroborates this finding. In other words, contrary to previous beliefs (not experimental research), continuously displaying messages did not make drivers more blind for changes in electronic messages at all. Indeed, it is likely that a certain amount of change blindness applies for changes in variable traffic signs (Harms and Brookhuis, 2012), as it does for static traffic signs (Charlton and Starkey, 2013; Martens and Fox, 2007). However, contrary to what is expected based on change blindness theory, both the current study as well as other studies on electronic signs (Harms and Brookhuis, 2014; Jamson and Merat, 2007), showed there was no evidence for reduced perception of signs when these were preceded by other active signs.
|Publication status||Published - 2016|
|Event||European Conference on Human Centred Design for Intelligent Transport Systems - Loughborough University, Loughborough, United Kingdom|
Duration: 30-Jun-2016 → 1-Jul-2016
|Conference||European Conference on Human Centred Design for Intelligent Transport Systems|
|Period||30/06/2016 → 01/07/2016|