AbstractStudies comparing results captured in a simulator with those on road are important to validate the approach but are scarce in the context of secondary task distraction due to the potential ramifications of diverting attention away from safe driving. The authors compare distraction‐related data from two studies exploring human–machine interfaces (HMI) design: one conducted in a static, medium‐fidelity driving simulator with a vehicle enclosure and immersive visual environment, and one conducted on road. In both, 19 drivers undertook an identical selection of touchscreen, point‐and‐select tasks. The magnitude of visual distraction (defined as off‐road glances directed towards the touchscreen) differed between the road and the simulator, with drivers making more and longer off‐road glances when interacting with the interface on road. However, the ordering of effects in response to changes to the complexity of interface design was the same. For example, the number and duration of off‐road glances increased with increasing number of interface elements, and smaller targets attracted longer off‐road glances, in both the road and simulator studies. The work demonstrates good relative validity for the use of medium‐fidelity driving simulators for HMI‐visual distraction testing, supporting their application in this context, and adds to the literature regarding the visual demand characteristics of in‐vehicle interfaces.

Camera-based digital mirrors purport to offer a range of benefits yet may influence drivers’ ability to quickly and accurately extract salient information pertaining to driving. In an on-road study, fifteen experienced drivers (seated in the front, left, passenger seat) undertook an orientation- discrimination task requiring the extraction of real-world information using either a digital mirror (placed internally) or a conventional, external, reflective mirror. Participants were asked to complete each task as quickly and accurately as possible, and then return their attention to the driving scene, as if they were driving. Although there was no difference in performance accuracy or reported workload between conditions, participants responded sooner when using the digital mirror – suspected to be due to the wider field-of-view intrinsic to its design, although participants also reported feeling “rushed” when using the digital mirror. The majority of participants (9 out of 15) indicated a preference for the conventional mirror, raising numerous concerns associated with the digital mirror, relating to image quality, field-of-view, focal depth (particularly for wearers of varifocal or reading glasses), and potential deleterious effects of ambient weather conditions, demonstrating important human factors issues still requiring attention in this context.

Digital mirrors within vehicles may improve aerodynamics and the field of view. Nevertheless, digital technology may fail. This study investigated the influences of different failures on distraction and behavioural adaptation, measured using glance and driving behaviour, as well as a workload questionnaire. Three failure conditions included a blank (no information), a degraded (hard to extract information), and a frozen (misleading information) display. In a high-fidelity simulator, 30 participants undertook three drives in a UK motorway scenario. During the second drive, the right (offside) digital mirror failed during the instruction to conduct a left-right lane-change manoeuvre, and remained until the end of that drive. Results show that failures led to longer and more glances towards the driver-side mirror, increased variability of speed and lateral position, and heightened workload; however, these distracting and behavioural effects lessened in future drives. Behavioural adaptations in the form of increased rear-view mirror or blind-spot checks could not be established. There were indications that the blanked mirror affected workload less than the other failures.

Whilst diary studies are often analysed in a qualitative manner, quantitative methods which analyse the percentage of different types of language used in diary entries, now exist. From a driving perspective, this could arguably tell us more about the underlying psychological processes occurring when drivers reflect on their on-road experiences. As part of a larger project, the current study used a quantitative method of language analysis, known as word count analysis, to compare driver diaries in which positive and negative driving events were reflected upon. Results suggested that when describing positive events, drivers discuss them with more elaborate and descriptive language and focus on certainty and goal-driven processes. Negative events, however, had more of a social focus as indicated by an increased use of function words. These findings provide insights into the ways in which positive and negative driving events may be appraised. Additionally, drivers used more words indicating control and reward when describing positive driving events; this is discussed in consideration of how word count analyses can provide further insight into psychological process associated with emotion, such as appraisals. (C) 2020 Elsevier Ltd. All rights reserved.

For adaptive cruise control (ACC) systems to be accepted and used safely, the transitions from cruise control mode to necessary driver intervention need to be obvious to the driver. Previous research shows that drivers have natural boundaries for acceptable values for time headway and time to collision to a car in front, which define at what point they are likely to step on the brake pedal. These boundaries can define an intuitive limit for ACC engagement. However, such boundaries may not be the same for all drivers, and not even for the same driver, whose goals may vary. The present research aimed to measure mental model boundaries in the context of different goals with a motorway cut-in scenario in a driving simulator. Participants drove in three conditions, after being asked to 'drive safely, 'drive fuel-efficiently' and after no specific instructions. The results show that both the safe and eco-driving instructions led drivers to brake at longer safety margins. These findings indicate that, as drivers follow different goals, e.g. as they are reminded to drive safely or eco-friendly, their preferences for operational limits of ACCs may change. This needs to be taken into account for design decisions, e.g. using 'safe' and 'eco' modes when driving.

Two studies investigated the concept of following a lead vehicle as a navigational aid. The first video-based study (n=34) considered how drivers might use a real-world lead vehicle as a navigational aid, whist the second simulator-based study (n=22) explored how an Augmented Reality (AR) virtual car, presented on a head-up display (HUD), may aid navigation around a complex junction. Study 1 indicated that a lead vehicle is most valued as a navigation aid just before/during a required maneuver. During the second study the dynamic virtual car (which behaved like a real vehicle) resulted in greater confidence and lower workload than a static virtual car that "waits" at the correct junction exit, but resulted in more gaze concentration. It is concluded that a virtual car may be a valuable element of a navigation system, in combination with other forms of information, to completely fulfil all a driver's navigational task requirements.

The visual demand of finger-touch based interactions with touch screens has been increasingly modelled using Fitts' Law. With respect to driving, these models facilitate the prediction of mean glance duration and total glance time with an index of difficulty based on target size and location. Strong relationships between measures have been found in the controlled conditions of driving simulators. The present study aimed to validate such models in naturalistic conditions. Nineteen experienced drivers carried out a range of touchscreen button-press tasks in an instrumented car on a UK motorway. In contrast with previous simulator-based work, our on-road data produced much weaker relationships between the index of difficulty and glance times. The model improved by focusing on tasks that required one glance only. Limitations of Fitts' Law in the more complex and dynamic real-world driving environment are discussed, as are the potential drawbacks of driving simulators for conducting visual demand research.

Specific vehicle automation use-cases such as traffic jams will be the first level 3 functions on the market. When the 'traffic jam pilot' nears its limits in non-critical situations, control needs to be handed back to the driver, enabling appropriate situation awareness (SA) and vehicle handling. According to previous research, operational vehicle stabilisation can be achieved within a transfer-of-control (TOC) of a few seconds in simple traffic environments, but tactical level decisions benefit from longer hand-over times. To date, the effects of non-critical TOCs have not been studied using set time frames. To investigate the impact of short (unplanned, 5 seconds) and long (planned, 50 seconds) TOC requests, while playing/not playing an engaging tablet game, a simulator experiment was conducted with 16 participants. Comparisons of the 60-second-period of manual driving following automation suggest better longitudinal vehicle control as well as more appropriate SA following the long TOC request, and automation periods without the game. However, following no engaging game, lateral performance was worse during the first 10 seconds of manual driving. Control-level visual search patterns did not change with TOC time or the game. Future research needs to consider support for driver's SA maintenance and readiness to drive following high automation.

Passenger cars contribute 12% of the overall carbon dioxide emissions in the EU. Eco-driving skills such as avoiding excessive braking and accelerating could reduce passenger car fuel consumption by up to 10% and consequently reduce vehicular emissions. However, educational material and the prospect of saving a considerable amount of money in the long-term do not change the behaviour of the majority of drivers. Little is known about drivers' current understanding of eco-driving, how they make decisions to put this knowledge into practice and what motivates them to do so. For this research drivers’ knowledge, behavioural rules and skill were tested in an experiment. Sixteen participants drove the University of Leeds desktop driving simulator on a varied road layout. Each participant was asked to drive four times, having had different instructions. These instructions were ‘Drive normally’ for the first and the last run; ‘Drive safely’ and ‘Drive fuel-efficiently’ in the remaining two. Each time they were presented with an urban setting with traffic lights as well as with busy traffic on a motorway. By finding out more about drivers' mental models of eco-driving and how they put them into practice, it will be possible to design more targeted and effective support systems.

ABSTRACT Specific vehicle automation use-cases such as traffic jams will be the first level 3 functions on the market. When the ‘traffic jam pilot’ nears its limits in non-critical situations, control needs to be handed back to the driver, enabling appropriate situation awareness (SA) and vehicle handling. According to previous research, operational vehicle stabilisation can be achieved within a transfer-of-control (TOC) of a few seconds in simple traffic environments, but tactical level decisions benefit from longer hand-over times. To date, the effects of non-critical TOCs have not been studied using set time frames. To investigate the impact of short (unplanned, 5 seconds) and long (planned, 50 seconds) TOC requests, while playing/not playing an engaging tablet game, a simulator experiment was conducted with 16 participants. Comparisons of the 60-second-period of manual driving following automation suggest better longitudinal vehicle control as well as more appropriate SA following the long TOC request, and automation periods without the game. However, following no engaging game, lateral performance was worse during the first 10 seconds of manual driving. Control-level visual search patterns did not change with TOC time or the game. Future research needs to consider support for drivers’ SA maintenance and readiness to drive following high automation.

Two studies investigated the concept of following a lead vehicle as a navigational aid. The first video-based study (n=34) considered how drivers might use a real-world lead vehicle as a navigational aid, whist the second simulator-based study (n=22) explored how an Augmented Reality (AR) virtual car, presented on a head-up display (HUD), may aid navigation around a complex junction. Study 1 indicated that a lead vehicle is most valued as a navigation aid just before/during a required maneuver. During the second study the dynamic virtual car (which behaved like a real vehicle) resulted in greater confidence and lower workload than a static virtual car that “waits” at the correct junction exit, but resulted in more gaze concentration. It is concluded that a virtual car may be a valuable element of a navigation system, in combination with other forms of information, to completely fulfil all a driver's navigational task requirements.

Full windshield displays (WSDs) have the potential to present imagery across the windshield. Current knowledge on display location has not investigated translucent displays at high eccentricities from the driver's forward view. A simulator study (n=26) was conducted aiming to, (a) investigate the effects of Head-Up Display (HUD) location across the entire windshield on driving performance, and (b) better understand how the visual demand for a complex HUD imagery differs from that for a Head-Down Display (HDD). Lane-keeping was poorer when HUD imagery was furthest from the driver (and for the HDD compared to the HUD). Equally, counts of "unacceptable" driving behaviour were greater for displays furthest from the driver's forward view. Furthermore, drivers preferred HUD imagery that was closer to them. The results indicate that HUD evaluations should account for image location, because of how driver gaze location can impact lateral driving performance.

Although drivers gain experience with age, many older drivers are faced with age-related deteriorations that can lead to a higher crash risk. Head-Up Displays (HUDs) have been linked to significant improvements in driving performance for older drivers by tackling issues related to aging. For this study, two Augmented Reality (AR) HUD virtual car navigation solutions were tested (one screen-fixed, one world-fixed), aiming to improve navigation performance and reduce the discrepancy between younger and older drivers by aiding the appropriate allocation of attention and easing interpretation of navigational information. Twenty-five participants (12 younger, 13 older) undertook a series of drives within a medium-fidelity simulator with three different navigational conditions (virtual car HUD, static HUD arrow graphic, and traditional head-down satnav). Results showed that older drivers tended to achieve navigational success rates similar to the younger group, but experienced higher objective mental workload. Solely for the static HUD arrow graphic, differences in most workload questionnaire items and objective workload between younger and older participants were not significant. The virtual car led to improved navigation performance of all drivers, compared to the other systems. Hence, both AR HUD systems show potential for older drivers, which needs to be further investigated in a real-world driving context.

This paper reports on two studies investigating how following a lead vehicle could act as a metaphor for an Augmented Reality (AR) system to support navigation tasks. For the first formative study, 34 participants completed a video-based evaluation of the role of a real lead vehicle when navigating a coherent journey. Verbal protocols indicated that a lead vehicle may be a valuable navigation aid at a range of different junction types, but not where drivers may desire a preview of upcoming steps or their overall orientation. A subsequent driving simulator study with 22 participants examined whether an AR lead vehicle may support drivers when navigating at complex junctions, specifically large multi-exit roundabouts. The virtual car led to good navigation and driving performance, which was comparable to a more traditional screen-fixed interface. Overall, this work demonstrates that a virtual lead vehicle may be beneficial within AR navigation devices.

Tangible incentives, training and feedback systems have been shown to reduce drivers' fuel consumption in several studies. However, the effects of such tools are often short-lived or dependent on continuous cues. Several studies found that many drivers already possess eco-driving mental models, and are able to activate them, for instance when an experimenter asks them to "drive fuel-efficiently". However, it is unclear how sustainable mental models are. The aim of the current study was to investigate the resilience of drivers' eco-driving mental models following engagement with a workload task, implemented as a simplified version of the Twenty Questions Task (TQT). Would drivers revert to 'everyday' driving behaviours following exposure to heightened workload? A driving simulator experiment was conducted whereby 15 participants first performed a baseline drive, and then in a second session were prompted to drive fuel-efficiently. In each drive, the participants drove with and without completing the TQT. The results of two-way ANOVAs and Wilcoxon signed-rank tests support that they drive more slowly and keep a more stable speed when asked to eco-drive. However, it appears that drivers fell back into 'everyday' habits over time, and after the workload task, but these effects cannot be clearly isolated from each other. Driving and the workload task possibly invoked unrelated thoughts, causing eco-driving mental models to be deactivated. Future research is needed to explore ways to activate existing knowledge and skills and to use reminders at regular intervals, so new driver behaviours can be proceduralised and automatised and thus changed sustainably. (C) 2018 Elsevier Ltd. All rights reserved.

Eco-driving campaigns have traditionally assumed that drivers lack the necessary knowledge and skills and that this is something that needs rectifying. Therefore, many support systems have been designed to closely guide drivers and fine-tune their proficiency. However, research suggests that drivers already possess a substantial amount of the necessary knowledge and skills regarding eco-driving. In previous studies, participants used these effectively when they were explicitly asked to drive fuel-efficiently. In contrast, they used their safe driving skills when they were instructed to drive as they would normally. Hence, it is assumed that many drivers choose not to engage purposefully in eco-driving in their everyday lives. The aim of the current study was to investigate the effect of simple, periodic text messages (nine messages in 2 weeks) on drivers' eco- and safe driving performance. It was hypothesised that provision of eco-driving primes and advice would encourage the activation of their eco-driving mental models and that comparable safety primes increase driving safety. For this purpose, a driving simulator experiment was conducted. All participants performed a pre-test drive and were then randomly divided into four groups, which received different interventions. For a period of 2 weeks, one group received text messages with eco-driving primes and another group received safety primes. A third group received advice messages on how to eco-drive. The fourth group were instructed by the experimenter to drive fuel-efficiently, immediately before driving, with no text message intervention. A post-test drive measured behavioural changes in scenarios deemed relevant to eco- and safe driving. The results suggest that the eco-driving prime and advice text messages did not have the desired effect. In comparison, asking drivers to drive fuel-efficiently led to eco-driving behaviours. These outcomes demonstrate the difficulty in changing ingrained habits. Future research is needed to strengthen such messages or activate existing knowledge and skills in other ways, so driver behaviour can be changed in cost-efficient ways.

Eco-driving has the potential to reduce fuel consumption and therefore emissions considerably. Previous research suggests that drivers have a certain level of eco-driving knowledge and skills, which they refrain from practising in their everyday lives. At the same time misconceptions and ambiguous messages from eco-driving support systems can confuse and demotivate. This research aimed to identify the mental models of eco-driving that regular drivers have. A driving simulator experiment with a varied road layout comprising urban and motorway sections was designed. The study used simple driving task instructions to investigate changes in the participants' behaviour and thoughts in three conditions. Sixteen drivers were asked to 'Drive normally', 'Drive safely' or 'Drive fuel-efficiently'. Behavioural measures, think aloud protocols and interviews were compared and analysed. The emphasis of this study was on eco-driving relevant indicators such as accelerating, braking, coasting and car-following. The results show that the participants do have mental models of eco-driving, which they did not use in the Baseline drive, when they were instructed to 'Drive normally'. Misconceptions about speed and travel time provide the potential for more effective communication with the driver about the momentary efficient speed as well as resulting time losses and fuel savings. In addition, in-vehicle guidance can increase driving safety compared to practicing eco-driving without them. (C) 2015 Elsevier Ltd. All rights reserved.