a b s t r a c tVariable speed limits (VSL) are used more commonly around the globe lately. Although on a macroscopic level positive effects of VSLs have been reported, the caveat is that the impact of VSLs is very sensitive to the level of driver compliance. Thus far it is unknown whether all individual drivers are actually able to notice when a speed limit changes into another speed limit; a prerequisite for purposeful speed limit compliance in the first place. To simulate regular driving conditions, twenty-four participants were familiarised with a particular route by driving the same route in a driving simulator nineteen times on five separate days. Part of the route consisted of a motorway where VSL signs were regularly displayed above every driving lane. At drive nineteen, speed limits changed from 80 km/ h to 100 km/h on four out of eight consecutive signs. After passing all signs, one expects 6.25% of the participants still to be unaware that the speed limit had increased (based on chance), while the results showed most participants had failed to notice the speed limit change (58.3%). Instead, they saw what they expected to see: a speed limit of 80 km/h. If the speed change had been vice versa, in other words from 100 km/h to 80 km/h, this would immediately result in speed offences, though not deliberately at all.

Pedestrians are commonly engaged in other activities while walking. The current study assesses (1) whether pedestrians are sufficiently aware of their surroundings to successfully negotiate obstacles in a city, and (2) whether various common walking practices affect awareness of obstacles and, or, avoidance behavior. To this end, an obstacle, i.e., a signboard was placed on a pavement in the city centre of Utrecht, the Netherlands. The behavioral measure consisted of the distance to the signboard before pedestrians moved to avoid it. After passing, participants were interviewed to obtain thought samples, self-reported route familiarity, a confirmation of secondary task engagement, and to assess awareness through recall and recognition of the signboard and its text. In this study 234 pedestrians participated. More than half of the participants (53.8%) was unaware of the signboard, still none of them had bumped into it. Mind wandering, being engaged in secondary tasks such as talking with a companion or using a mobile phone, and being familiar with a route, did not affect awareness nor avoidance behavior. In conclusion, despite being very common there was no evidence that walking without awareness necessarily results in risk. The absence of awareness does not imply any absence of cognitive and perceptual processing. Pedestrians are still capable of successfully avoiding obstacles in their path, even in visually more challenging environments such as a city centre. It is argued that this is because walking consists of highly automated, skilled behavior.

No abstract

Road authorities struggle with the question whether variable message signs (VMSs) should exclusively be used for traffic management or could also be used to display traffic-irrelevant messages, such as mottos or commercial advertisements. The current study assesses behavioural responses to a critical route instruction displayed on the same VMS that previously displayed a variety of traffic-irrelevant messages. For this, thirty-two participants were divided between a control group and an experimental group (the advertisements group). In a driving simulator, all were familiarised with the same route by driving a VMS-equipped motorway nine times. For the advertisements group, up to drive 8, this VMS displayed various advertisements. Whereas for the control group it was blank. In the 9 th drive, the VMS displayed a critical detour message for all participants. This critical route instructioninforming drivers to take the nearest exitresulted in compliant driver behaviour in the advertisements group. In addition, they only reduced speed marginally to increase the time to process the VMS text. The control group, on the contrary, displayed a much sharper speed reduction; though the instruction only moderately altered motorway exit behaviour. What is more, the 31% (n = 4) of the advertisements group who complied with the critical route instruction subsequently failed to recall this message (recalling an advertisement instead). In conclusion, this study provides evidence that displaying traffic-irrelevant messages on VMSs might not interfere with traffic management; provided the format of said messages is in accordance with ergonomic VMS guidelines as used in this study. It is proposed that due to repeated exposure to various VMS texts, reading the sign has been practised to the extent that little to no conscious deliberation was required. As a result, recall of what was seen, proved to be an inadequate proxy for assessing driver behaviour. This study shows that conscious attention might not be a prerequisite for compliance. Furthermore, it suggests that continuous variability in objects in the traffic environment may become part of a subconscious monitoring process, as long as they have been sufficiently practised.