The development of eXtended Reality (XR) technologies has led to an increase in the use of virtual spaces to help support collaboration. However, collaboration between physical and virtual environments is often considered solely with respect to how successfully the XR technology has been used to integrate virtual and physical worlds. In contrast, this study explored how participants collaborated within a Blended Reality (BR) system, with the overall aim of identifying the benefits and challenges associated with BR systems during group collaboration. Analysis of interview and video observations highlighted various beneficial affordances and considerations associated with different elements of the BR system. There were benefits associated with the physical, virtual and blended space as well as considerations relating to the task design and system design. Further work should seek to determine how to design BR spaces to better suit the collaborative context.

Considering that a significant portion of the current pedestrian population has limited exposure to automated vehicles (AVs), it is crucial to have a reliable instrument for assessing pedestrians’ initial trust in AVs. Using a survey of 436 pedestrians, this study developed and validated a PITQA (Pedestrians’ Initial Trust Questionnaire for AVs) scale using partial least squares structural equation modeling (PLS-SEM). The proposed scale will be valuable in monitoring the progression of trust over time and considering trust-related factors during the design process. The results revealed that seven key constructs significantly contribute to predicting initial trust between pedestrians and AVs. These constructs include propensity to trust, perceived statistical reliability, dependability and competence, perceived predictability, familiarity, authority/subversion, care/harm, and sanctity/degradation. These shed light on how the trust propensity of individuals, different trust/trustworthiness attributes might constitute different aspects of initial trust in the pedestrian-AV context. The developed scale can be a potentially useful tool for future research endeavors concerning trust calibration and the design of AVs specifically tailored for vulnerable road users.

Automated vehicles (AVs) are one critical application area of artificial intelligence (AI). However, a lack of appropriate trust can be a major barrier to successfully introducing AVs into the market. The objective of this study is to summarize and synthesize the existing literature to gain a greater understanding of factors that will potentially influence the development of pedestrians’ trust in AVs over time. Since AVs will become part of a larger infrastructure system that influences more than just AV users, they should also be accepted by pedestrians and other road users. There is a need for pedestrians to form appropriate levels of trust toward AVs to achieve safe interaction with such vehicles in circumstances characterized by uncertainty and vulnerability. Consequently, factors relevant to the building of this appropriate trust must be understood. By integrating the reviewed empirical studies and related theories, a theoretical model has been proposed and developed, comprising three layers of variability in pedestrian-AV trust (dispositional trust, situational trust, and learned trust). Given that this is an emerging field of research, much still remains unknown, and this review identifies several gaps in current knowledge for each layer of trust, as well as providing suggestions for consideration in future studies. Additionally, the proposed model of pedestrian-AV trust can be useful to transportation researchers, practitioners, designers, and AV manufacturers for designing AVs and related transportation systems for the purposes of successfully integrating AVs into society, and calibrating pedestrians’ trust to the appropriate level.

Augmented reality (AR) offers new ways to visualize information on-the-go. As noted in related work, AR graphics presented via optical see-through AR displays are particularly prone to color blending, whereby intended graphic colors may be perceptually altered by real-world backgrounds, ultimately degrading usability. This work adds to this body of knowledge by presenting a methodology for assessing AR interface color robustness, as quantitatively measured via shifts in the CIE color space, and qualitatively assessed in terms of users' perceived color name. We conducted a human factors study where twelve participants examined eight AR colors atop three real-world backgrounds as viewed through an in-vehicle AR head-up display (HUD); a type of optical see-through display used to project driving-related information atop the forward-looking road scene. Participants completed visual search tasks, matched the perceived AR HUD color against the WCS color palette, and verbally named the perceived color. We present analysis that suggests blue, green, and yellow AR colors are relatively robust, while red and brown are not, and discuss the impact of chromaticity shift and dispersion on outdoor AR interface design. While this work presents a case study in transportation, the methodology is applicable to a wide range of AR displays in many application domains and settings.

Currently, the visual demand incurred by vehicle displays is evaluated using time criteria (such as those provided by NHTSA). This 60-participant driving simulator study investigated to what extent glance time criteria applies to Head-up Display (HUD) imagery, considering 48 locations across the windshield (and 3 in-vehicle display positions). Participants were required to make a long controlled continuous glance to a sample of these locations. Consequently, the time at which lateral/longitudinal unsafe driving occurred (e.g. deviating out of lane, unacceptable time to collision) could then be assessed. Using the selected measures, the results suggest that drivers are able to maintain driving performance for longer than recommended NHTSA guidelines for in-vehicle displays whilst engaging with HUD imagery in various locations. Importantly, the data from this study provides initial maps for designers highlighting the visual demand implications of HUD imagery across the windshield.

In a longitudinal study, 49 drivers undertook a commute-style journey, with part of the route supporting level-3 automation, over five consecutive days. Bespoke HMIs were provided to keep drivers in-the-loop during automation, and help them regain situational-awareness (SA) during handovers, in a 2×2 between-subjects design. Drivers demonstrated high levels of trust from the outset, delegating control to the vehicle (when available) and directing attention to their own activities/devices. Ratings of trust and technology acceptance increased during the week -- even following an unexpected, emergency handover on day four -- with the highest ratings recorded on day five. High levels of lateral instability were observed immediately following takeovers, although improvements were noted during the week and following the provision of SA-enhancing hand-over advice. Results demonstrate benefits associated with novel HMI designs to keep drivers in-the-loop and improve takeover performance, as well as the necessity of multiple exposures during the evaluation of future, immersive technologies.

Recognising that one of the aims of conversation is to build, maintain and strengthen positive relationships with others, the study explores whether passengers in an autonomous vehicle display similar behaviour during transactions with an on-board conversational agent-interface; moreover, whether related attributes (e.g. trust) transcend to the vehicle itself. Employing a counterbalanced, within-subjects design, thirty-four participants were transported in a self-driving pod using an expansive testing arena. Participants undertook three journeys with an anthropomorphic agent-interlocutor (via Wizard-of-Oz), a voice-command interface, or a traditional touch-surface; each delivered equivalent task-related information. Results show that the agent-interlocutor was the most preferred interface, attracting the highest ratings of trust, and significantly enhancing the pleasure and sense of control over the journey experience, despite the inclusion of 'trust challenges' as part of the design. The findings can help support the design and development of in-vehicle agent-based voice interfaces to enhance trust and user experience in autonomous cars.

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.

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.

Employing a 2x2 within-subjects design, forty-eight experienced drivers (28 male, 20 female) undertook repeated button selection and 'slider-bar' manipulation tasks, to compare a traditional touchscreen with a virtual mid-air gesture interface in a driving simulator. Both interfaces were tested with and without haptic feedback generated using ultrasound. Results show that combining gestures with mid-air haptic feedback was particularly promising, reducing the number of long glances and mean off-road glance time associated with the in-vehicle tasks. For slider-bar tasks in particular, gestures-with-haptics was also associated with the shortest interaction times, highest number of correct responses and least 'overshoots', and was favoured by participants. In contrast, for button-selection tasks, the touchscreen was most popular, enabling the highest accuracy and quickest responses, particularly when combined with haptic feedback to guide interactions, although this also increased visual demand. The study shows clear potential for gestures with mid-air ultrasonic haptic feedback in the automotive domain.

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.

Touchscreen human–machine interfaces (HMIs) are commonly employed as the primary control interface and touch-point of vehicles. However, there has been very little theoretical work to model the demand associated with such devices in the automotive domain. Instead, touchscreen HMIs intended for deployment within vehicles tend to undergo time-consuming and expensive empirical testing and user trials, typically requiring fully functioning prototypes, test rigs, and extensive experimental protocols. While such testing is invaluable and must remain within the normal design/development cycle, there are clear benefits, both fiscal and practical, to the theoretical modeling of human performance. We describe the development of a preliminary model of human performance that makes a priori predictions of the visual demand (total glance time, number of glances, and mean glance duration) elicited by in-vehicle touchscreen HMI designs, when used concurrently with driving. The model incorporates information theoretic components based on Hick–Hyman Law decision/search time and Fitts’ Law pointing time and considers anticipation afforded by structuring and repeated exposure to an interface. Encouraging validation results, obtained by applying the model to a real-world prototype touchscreen HMI, suggest that it may provide an effective design and evaluation tool, capable of making valuable predictions regarding the limits of visual demand/performance associated with in-vehicle HMIs, much earlier in the design cycle than traditional design evaluation techniques. Further validation work is required to explore the behavior associated with more complex tasks requiring multiple screen interactions, as well as other HMI design elements and interaction techniques. Results are discussed in the context of facilitating the design of in-vehicle touchscreen HMI to minimize visual demand.

We consider the potential for novel in-vehicle user-interfaces that alter speed perception at a subliminal level through the spatial adaption of music. In a fixed-base simulator, twenty-six participants drove on a motorway and were asked to maintain a speed of 70mph. At specific points, the speedometer was turned off. Music at a constant tempo was played throughout but periodically changed in balance from a 50:50 front:rear speaker split to a 25:75 ratio. Without the speedometer, participants drove significantly slower after the music had faded from the front to rear speakers (mean speed 71.5mph) compared to when no change occurred (mean speed 73.1mph). Post study interviews revealed that participants were not aware of alterations in the spatial positioning of the music. Such results suggest drivers naturally slowed when the music faded from front to rear speakers in an unconscious attempt to re-envelope themselves within the sound bubble.

Unencumbered by the need to provide permanent manual control, future autonomous vehicles may be absent of traditional driving elements, such as a steering wheel and foot-pedals. While this provides additional space/comfort for drivers, an alternative device/s, that enables quick and effective manual control recovery, may still be required. Twenty participants, comprising an equal number of 'Drivers' and 'Non-Drivers', undertook two drives utilising a medium-fidelity simulator in which the original steering wheel and pedal-set were removed/deactivated. Participants controlled the vehicle using a centrally-mounted joystick in 2 scenarios: following an unexpected take-over request and during an extended period of manual driving. Results show that both groups rated the technology positively and were generally capable of manoeuvring the vehicle. Nevertheless, the groups differed in the way that performance was effected. For example, significant differences were evident in visual behaviour, resulting in 50% (n=5) of Non-Drivers colliding with another vehicle following transfer of control.

In-vehicle support systems have the potential to reduce the risk of pedestrian collisions and promote gains in braking performance and visual attention when scanning for threats on the road. This study investigated changes in driver behavior in pedestrian collision scenarios with increasing urgency while using varying levels of pedestrian alert system (PAS) support in a medium fidelity driving simulator. During pedestrian collision scenarios, we assessed drivers' eye gaze behavior, braking performance, and acceptance ratings across three levels of PAS and four levels of increasing urgency, defined as time to collision (TTC). Results suggest that both audio- and visually-based PAS do not produce gains in the localization of pedestrians, but can nevertheless improve drivers' braking performance in events where pedestrians may pose a threat. Our results further suggest that drivers exhibit both innate and direct confidence in visually-based PAS support, despite no concurrent gains in visual scanning performance.

This paper explores how navigational guidance which references the world around the driver influences their experience of workload and environmental engagement on multiple journeys. In an on-road study thirty participants drove following three intersecting routes in the city of Nottingham, UK on two separate occasions, one week apart. In a between subjects design, participants followed navigational guidance from either: an existing navigation system (SatNav); or the semi-structured wayfinding prompts of an informed passenger. Results indicated that drivers following the navigational guidance of the informed passenger benefitted from lower workload overall which also reduced significantly on their second drive. Additionally, these drivers made significantly fewer errors on route and demonstrated superior survey knowledge compared to their SatNav counterparts. This evidence supports the case for enhanced route directions in future navigation devices, referencing the driver's environment in a manner that can reduce workload and navigation errors, whilst assisting in spatial knowledge development.

Windshield displays (WSDs) are the big siblings of Head-up displays (HUDs). They are assumed to cover the entire windshield and to allow displaying content at continuous depth, eventually. This creates a large and unstructured 3D space for information display -- raising the question what to display where. To address this question, we developed a view management concept for WSDs in left hand drive cars which proposes zones and areas for specific information. As driving is a safety-critical task, we designed the initial concept with the driver's perceptual abilities in mind. Subsequently, we gathered insights into the driver's needs and desires from a formative study. We asked participants where they would place different types of information after inspiring their imagination by a 3D driving scene and WSD information on a Google Cardboard. The improved concept respects both the drivers' needs and desires and their perceptual abilities and can serve as a basis for view management concepts of future WSD.

Given the proliferation of digital assistants in everyday mobile technology, it appears inevitable that next generation vehicles will be embodied by similar agents, offering engaging, natural language interactions. However, speech can be cognitively captivating. It is therefore important to understand the demand that such interfaces may place on drivers. Twenty-five participants undertook four drives (counterbalanced), in a medium-fidelity driving simulator: 1. Interacting with a state-of-the-art digital driving assistant ('DDA') (presented using Wizard-of-Oz); 2. Engaged in a hands-free mobile phone conversation; 3. Undertaking the delayed-digit recall ('2-back') task and 4. With no secondary task (baseline). Physiological arousal, subjective workload assessment, tactile detection task (TDT) and driving performance measures consistently revealed the '2-back' drive as the most cognitively demanding (highest workload, poorest TDT performance). Mobile phone and DDA conditions were largely equivalent, attracting low/medium cognitive workload. Findings are discussed in the context of designing in-vehicle natural language interfaces to mitigate cognitive demand.

Touchscreen Human-Machine Interfaces (HMIs) inherently demand some visual attention. By employing a secondary device, to work in unison with a touchscreen, some of this demand may be alleviated. In a medium-fidelity driving simulator, twenty-four drivers completed four typical in-vehicle tasks, utilising each of four devices -- touchscreen, rotary controller, steering wheel controls and touchpad (counterbalanced). Participants were then able to combine devices during a final 'free-choice' drive. Visual behaviour, driving/task performance and subjective ratings (workload, emotional response, preferences), indicated that in isolation the touchscreen was the most preferred/least demanding to use. In contrast, the touchpad was least preferred/most demanding, whereas the rotary controller and steering wheel controls were largely comparable across most measures. When provided with 'free-choice', the rotary controller and steering wheel controls presented as the most popular candidates, although this was task-dependent. Further work is required to explore these devices in greater depth and during extended periods of testing.

This study explored the effects that augmented reality graphics have on a drivers' distance estimation/depth perception in an augmented side view mirror. The study was conducted both inside a simulator and outside in a parking lot. Sixteen participants partook in the study, 8 in the simulator and 8 in the test vehicle outside. Distance judgments were compared across four side view mirror conditions both simulator and outdoor scenarios. Results show some opportunities for AR to improve depth judgments, but further analysis is necessary.

Augmenting navigation systems with landmarks has been posited as a method of improving the effectiveness of the technology and enhancing drivers’ engagement with the environment. However, good navigational landmarks are both laborious to collect and difficult to define. This research aimed to devise a game concept which could be played by passengers in cars, and would collect useful landmark data as a by-product. The paper describes how a virtual graffiti tagging game concept was created and tested during on-road trials with 38 participants. The data collected in the road trials were then validated using a survey, in which 100 respondents assessed the quality of the landmarks collected and their potential for reuse in navigation applications. Players of the game displayed a consensus in choosing where to place their graffiti tags, with over 30% of players selecting the same object to tag in 10 of the 12 locations. Furthermore, significant correlation was found between how highly landmarks were rated in the survey and how frequently they were tagged during the game. The research provides evidence that using crowdsourcing games to collect landmarks does not require large numbers of people, or extensive coverage of an area, to produce suitable candidate landmarks for navigation.

Using landmark-based navigation can greatly improve drivers' route-finding performance. Previous research in this area has tended to focus on the inclusion of text or icon-based landmark information utilising dashboard-mounted displays. In contrast, we present landmark-based navigation information using a Head-Up Display (HUD). A major issue with using landmarks for navigation is their inherent variability in quality, with many 'poor' candidates that are not easily identifiable or communicable. A proposed solution to improve the usefulness and utility of such landmarks is to highlight/enhance them using augmented reality (AR). Twenty participants undertook four drives in a driving simulator utilising an AR navigation system presented on a HUD. Participants were provided navigational instructions presented as either conventional distance-to-turn information, on-road arrows or augmented landmark information (arrow highlighting or box enclosing landmark adjacent to the required turning). Participants demonstrated significant performance improvements while using the AR landmark 'box' presentations compared to conventional distance-to-turn information, with response times and success rates enhanced by 43.1% and 26.2%, respectively. Moreover, drivers reported a significant reduction in workload when using the AR landmark 'boxes'. We conclude that there are significant benefits to providing navigational information utilising AR presentations of landmark information on a HUD.

Finger-touch based interactions with capacitive touchscreen devices in cars are becoming increasingly common. As such, it is critical to understand the basic human factors of target acquisition (pointing/touching) in this context. We describe a simulator study that aims to build Fitts' Law relationships for predicting the visual demands (mean glance duration and total glance time) associated with finger-touch pointing tasks as a function of target size, location and design. The observed data show strong linear relationships between all visual demand measures and Fitts' index of difficulty, indicating that finger-touch pointing tasks conform well with the Fitts' Law model under conditions of divided attention. The derived equations are discussed in the context of designing in-vehicle touchscreen interfaces for minimal visual demand.

Driver distraction is a major contributor to road traffic accidents. Consequently, NHTSA have published detailed guidelines intended to discourage the introduction of excessively distracting electronic devices in vehicles. However, concerns have been raised regarding the theoretical basis and ecological validity of the NHTSA Eye Glance Testing Using a Driving Simulator (EGDS) testing protocol. In particular, it has been noted that the driving scenario is over-simplified and acceptance is predicated on absolute measures determined from a poorly defined and out-dated reference task ('radio-tuning'). Using a medium-fidelity driving simulator, a new prototype touchscreen interface was evaluated in full compliance with the NHTSA EGDS test protocol. As a comparison, the same interface was then tested using a well-established ('standard') driving scenario. Results show that the different scenarios elicited significantly different visual behaviour with drivers placing more emphasis (extended TEORT and MGD) on secondary task performance during the NHTSA scenario. Furthermore, driving performance measures indicated higher levels of 'presence' associated with the 'standard' environment. Conclusions are drawn regarding the effect of primary task demand on secondary task performance and NHTSA-compliance, and the validity of the proposed test scenario and reference task.

Augmented reality (AR) adds virtual graphics, sounds or data to a real-world environment. Future Head-Up Displays in vehicles will enable AR images to be presented at varying depths, potentially enabling additional cues to be provided to drivers to facilitate task performance. In order to correctly position such AR imagery, it is necessary to know at what point the virtual image is discriminable in depth from a real-world object. In a two-alternative forced-choice psychophysical depth judgment task, 40 observers judged if an AR image (a green diamond) appeared in front or behind a static 'pedestrian' target. Depth thresholds for the AR image were tested with the pedestrian target at 5m, 10m, 20m and 25m and at six locations relative to the pedestrian. The AR image was presented at different heights in the visual field, (above, middle and below the real-world target) and across the horizontal plane (left, middle, right of the real-world target). Participants were more likely to report that the AR image was presented in front of the target rather than behind. Inconsistent with previous findings, no overall effects of height or horizontal position were found. Depth thresholds scaled with distance, with larger thresholds at further distances. Findings also showed large individual differences and slow response times (above 2.5s average), suggesting of difficulties judging AR in depth. Recommendations are made regarding where a HUD image should be located in depth if a designer wishes users to reliably perceive the image to be in front/alongside or behind a real-world object.

Occlusion is a popular technique used to evaluate the visual demand associated with secondary tasks/devices in a driving context offering a low cost, highly accessible alternative to driving simulators and on-road studies. Several standardised occlusion test protocols have been published, most notably by NHTSA and ISO. These differ significantly in terms of how many participants are deemed to be sufficient in order to elicit statistically representative behaviour, and thus impose different 'costs' on incumbent organisations. A NHTSA-compliant study investigated three navigation-related tasks using a smartphone app (APP) and portable navigation device (PND). As a comparison, 1000 iterations of 10 participant ISO sample groups were extracted from the NHTSA 24-participant cohort and analysed in accordance with the same measures. Results obtained using all 10-participant ISO groups were consistent with the NHTSA findings, indicating that both standards would support the same conclusions regarding relative performance. Applying NHTSA's acceptance criteria, it is evident that, in most cases, recommendations based on the smaller ISO samples would be the same as those obtained from the full NHTSA cohort. However, only 95.5% conformance was observed for task 3 using the PND, suggesting a small risk that different conclusions could be drawn for this particular device/task if a smaller number of participants were used. Given the lower inherent costs associated with the ISO protocol, we thus conclude that this may be better suited for relative/formative assessment, whereas the NHTSA protocol may be more appropriate for summative evaluations.

This study investigated the differences between head-up display (HUD) and head-down display (HDD) systems in vehicles with the ultimate goal of increasing driver performance and safety. Our initial focus was on comparing drivers' visual task performance (and associated driving behavior) while using a HUD and HDD. In a medium-fidelity driving simulator, 16 experienced drivers performed two types of tasks, a structured (text) and a semi-structured (grid) visual search task while driving. They first completed a baseline drive using a driving simulator with no secondary tasks followed by four drives under various conditions: HUD-Text, HUD-Grid, HDD-Text, and HDD-Grid. The study returned mixed results. HUDs generally contributed to more secondary task errors, but overall, users still preferred to use HUDs over HDDs. The response time to complete tasks was unevenly affected by display type. While there was no difference between response times in the grid tasks (HDD vs. HUD), the HUD was associated with significantly faster task performance as compared to the text tasks. These results suggest that HUDs may offer advantages to drivers in some task scenarios but more research is needed to understand under what conditions they do not add value.

We present an in-the-wild project to design and study a mobile musical soundtrack that enhances the experience of visiting a sculpture park. As with soundtracks for films and games, the goal was to enhance the emotional and narrative aspects of the experience while remaining in the background. We describe a compositional approach in which we first established a broad musical landscape before treating specific exhibits with detailed musical trajectories. Our study reveals how our soundtrack dramatically shaped visitors' experiences while they remained largely unaware of its operation. We distil seven experiential factors to be addressed by mobile soundtracks alongside ten compositional guidelines.

Recent research indicates that users consistently underestimate depth judgments to Augmented Reality (AR) graphics when viewed through optical see-through displays. However, to our knowledge, little work has examined how AR graphics may affect depth judgments of real world objects that have been overlaid or annotated with AR graphics. This study explores whether AR graphics have directional effects on users' depth perception of real-world objects. Participants were shown an initial target location and were then asked to indicate when a moving target was perceived to be at the previously specified target location. Each participant experienced three different display conditions: no AR visual display (control), a conformal AR graphic overlaid on the pedestrian via head-up display (HUD), and the same graphic presented on a tablet physically located on the pedestrian. The judged distance from the correct location was recorded, and after each trial, participants' confidence in determining the correct distance was captured. Across all conditions, participants underestimated the distance of the physical object. Greater variability was observed in the accuracy of distance judgments under the AR HUD condition relative to the other two display conditions. In addition, participant confidence levels were significantly lower in the AR HUD condition.

Recent research indicates that users consistently underestimate depth judgments to Augmented Reality (AR) graphics when viewed through optical see-through displays. However, to our knowledge, little work has examined how AR graphics may affect depth judgments of real world objects that have been overlaid or annotated with AR graphics. This study begins a preliminary analysis whether AR graphics have directional effects on users' depth perception of real-world objects, as might be experienced in vehicle driving scenarios (e.g., as viewed via an optical see-through head-up display or HUD). Twenty-four participants were asked to judge the depth of a physical pedestrian proxy figure moving towards them at a constant rate of 1 meter/second. Participants were shown an initial target location that varied in distance from 11 to 20 m and were then asked to press a button to indicate when the moving target was perceived to be at the previously specified target location. Each participant experienced three different display conditions: no AR visual display (control), a conformal AR graphic overlaid on the pedestrian via a HUD, and the same graphic presented on a tablet physically located on the pedestrian. Participants completed 10 trials (one for each target distance between 11 and 20 inclusive) per display condition for a total of 30 trials per participant. The judged distance from the correct location was recorded, and after each trial, participants' confidence in determining the correct distance was captured. Across all conditions, participants underestimated the distance of the physical object consistent with existing literature. Greater variability was observed in the accuracy of distance judgments under the AR HUD condition relative to the other two display conditions. In addition, participant confidence levels were considerably lower in the AR HUD condition.

Driving is a social task, where drivers commonly communicate with other road users (e.g. verbally, through gestures, etc.). This exploratory cross-cultural research sought to investigate various communication issues raised while driving, and how a hypothetical electronic device could address them. Twenty-four participants from the UK and Brazil were asked to give their opinions on how they would react to six different driving scenarios involving communication between drivers. The scenarios varied in who instigated the interaction, the number of vehicles involved, the likelihood of anonymity, the event duration and whether the vehicle was stationary/in motion. Results highlighted various cross-cultural differences between drivers when using traditional means of communication, e.g. use of horn/lights. For the electronic device, results showed how the main driver's reaction to an aggressive message would affect their decision to interact with another driver via the device. The presence of passengers was also believed to have important implications for how the system is likely to be used in practice. The study generated design recommendations for a driver-to-driver communication device, such as the need for non-visual interactions and a set of pre-defined messages to cover the basic communication scenarios.

Musical soundtracks will be important features of future locative experiences from tours to games. We present a study designed to uncover potential relationships between higher-level musical structures such as harmony, melody, timbre, dynamic intensity and punctuation and users' spatial experiences. We observed twenty-two participants exploring an open field while listening to four contrasting musical compositions, and then interviewed them afterwards. We report their different approaches to interpreting the music, strategies for mapping zones, choice of stopping destinations, and their awareness and appreciation of the music. Our discussion of these findings in relation to the literature leads us to propose six initial principles to guide the composition of mobile and locative soundtracks, and also to articulate a three-layer framework of global, regional and local attachment to help guide the attachment of musical features to different regions within a locative experience.

Touch screens are increasingly used within modern vehicles, providing the potential for a range of gestures to facilitate interaction under divided attention conditions. This paper describes a study aiming to understand how drivers naturally make swipe gestures in a vehicle context when compared with a stationary setting. Twenty experienced drivers were requested to undertake a swipe gesture on a touch screen in a manner they felt was appropriate to execute a wide range of activate/deactivate, increase/decrease and next/previous tasks. All participants undertook the tasks when either driving within a right-hand drive, medium-fidelity simulator or whilst sitting stationary. Consensus emerged in the direction of swipes made for a relatively small number of increase/decrease and next/previous tasks, particularly related to playing music. The physical action of a swipe made in different directions was found to affect the length and speed of the gesture. Finally, swipes were typically made more slowly in the driving situation, reflecting the reduced resources available in this context and/or the handedness of the participants. Conclusions are drawn regarding the future design of swipe gestures for interacting with in-vehicle touch screens.

Touchpads in vehicles offer a range of potential benefits over existing input devices, such as touchscreens. This article describes a study aiming to establish where a touchpad should be located within a right-hand drive vehicle. Sixteen participants (50:50 right/left handed) drove three routes in a right-hand drive simulator while following a lead vehicle at a perceived safe distance. At specific points, participants were asked to carry out three tasks of varying complexity using the touchpad. For each of the routes travelled, the touchpad was positioned in one of the three locations: in the centre console; in the door armrest and in the steering wheel. Differences in the performance and preferences of right-handed people vs. left-handed people were found. Right-handed people rated the door armrest location highly and made few glances towards this location while driving. In contrast, left-handed drivers were more positive towards the centre console location. The steering wheel location required a particularly high-visual demand. It is concluded that, for right-hand drive vehicles, a touchpad should be located in both the centre console and the door armrest to suit the diverse needs of the driver population.

Designers of in-vehicle computing systems must consider which input devices are most suitable for use in the safety-critical driving situation. This paper describes a study aiming to establish which tasks are best supported by an in-vehicle touchpad system. Eighteen participants (50:50 right/left handed) drove three routes in a right-hand drive simulator while following a lead vehicle at a perceived safe distance. At specific points, participants were asked to carry out seven tasks of varying qualities using a prototype touchpad system, a touchscreen or a rotary controller interface. Results indicated that participants were most negative (in terms of preferences and performance) with the rotary controller interface. Conversely, the results for the touchpad versus the touchscreen interfaces were clearly task dependent. For instance, with the touchpad, subjective opinions and objective performance were most positive for tasks in which simple commands enabled drivers to bypass the need for complex menu interactions (e.g. changing the interior temperature). In contrast, results for the touchscreen were evidently superior for simple menu selection tasks (e.g. selecting a preset radio station). Conclusions are drawn regarding the nature of tasks that are best suited to alternative input devices within vehicles and the potential for a touchpad/touchscreen solution.

With the increasing use of in-vehicle information systems (IVIS) by drivers whilst the vehicle is in motion, the risk of distraction-related crashes is expected to increase. Distraction in this case arises from engagement of the driver with the visual demand of an IVIS display, but measurement of such visual demand, and design decisions about how much visual demand is acceptable in this context, is problematic. Using the visual ‘occlusion’ technique, this paper uses data from visual demand metrics (from 4 reference in-vehicle tasks with 60 participants) and makes comparisons with several other approaches including expert usability analysis, other reference levels, social acceptability survey data, and a comparison with alcohol impairment. Based on these considerations an approach is taken to represent the distribution of occlusion measurements and a demand reference level (DRL) is proposed to be used as a criterion for design of IVIS displays. The DRL comprises a metric derived from occlusion measurements and an absolute value.

Sensory integration is critical to the perception of quality in automobile interior design. To investigate the relative contribution of the senses of vision, touch and hearing to the perception of quality for in-car switches, 30 participants rated eight switches taken from two vehicles when all senses were available and under various conditions of sensory deprivation: no hearing; no vision; no touch. Results indicated that touch had the greatest role to play in judgements of quality, enabling participants more easily to differentiate between the two vehicle designs. Furthermore, correlation and regression analyses for specific switches indicated that touch contributed up to three times as much to quality ratings compared to either the vision or hearing senses. Future research should aim to verify such findings and to establish which aspects of touch have particular influence.

Vehicle navigation systems aim to reduce the mental workload for drivers by automating elements of the driving task. Concern has been raised, however, that their long-term use may cause unforeseen problems, including suppressing cognitive map development.

To assess the potential distraction of In-Vehicle Information Systems (IVIS), simple, low cost evaluation methods are required for use in early design stages. The occlusion technique evaluates IVIS tasks in interrupted vision conditions, aiming to predict likely visual demand. However, the technique necessitates performance-focused user trials utilising robust prototypes, and consequently has limitations as an economic evaluation method. HCI practitioners view the Keystroke Level Model (KLM) as a reliable and valid means of modelling human performance, not requiring empirical trials or working prototypes. This paper proposes an extended KLM, which aims to predict measures based on the occlusion protocol. To validate the new method, we compared results of an occlusion study with predictions based on the assumptions of the extended KLM. Analysis revealed significant correlations between observed and predicted results (R=0.93-0.98) and low error rates (7-13%). In conclusion, the extended KLM shows considerable merit as a first-pass design tool.

Learning to program is a difficult process, and students that perform well in other subjects may not produce comparable results in programming. Evidence suggests that some programmers are inherently more skilled than others, and one individual difference that has been shown to be important is spatial ability. This cognitive characteristic is implicated in successful real-world navigation. It is also important for navigating within hypertext, and there is a growing recognition that it has a part to play in program comprehension and development, with navigation of source code considered similar to navigating in the real world. Little research has been carried out to study the navigational patterns of programmers with differing spatial skills. In this study, 24 students enrolled on a Masters in IT course at a University in the UK were given a code comprehension exercise. Various measures were made of time taken and movement around the code. Those with high spatial ability completed the task in shorter time, spent less time searching around deciding where to go next, and jumped more frequently within and between class files. Strong relations were also found between spatial ability and results in programming modules, with much weaker relations with non-programming modules. This paper discusses the implications of these results in relation to the accessibility of programming to learners with low spatial ability.

This paper outlines the arguments (and supporting evidence) both for and against allowing drivers to enter a destination with a vehicle navigation system while active in the primary driving task (‘on-the-move’). The benefits and limitations of various safety-related interventions are discussed, including the use of warnings/instructions, safeguards and design improvements. Whilst it is clear that the visual, manual and cognitive demands associated with entering destinations using current vehicle navigation systems can be high, it is concluded that inhibiting the use of this functionality whilst on-the-move, particularly through the use of reactionary legislation, will not be the ideal solution. Rather, human factors research must investigate the potential for novel user-interfaces, develop reliable and valid methods for assessing the safety impact of different designs, and consider the wider issues of system use and behavioural adaptation.