Tactile and Multisensory Spatial Warning Signals for Drivers

Post Take-Over Performance Varies in Drivers of Automated and Connected Vehicle Technology in Near-Miss Scenarios

OBJECTIVE

This study examined the impact of monitoring instructions when using an automated driving system (ADS) and road obstructions on post take-over performance in near-miss scenarios.

BACKGROUND

Past research indicates partial ADS reduces the driver's situation awareness and degrades post take-over performance. Connected vehicle technology may alert drivers to impending hazards in time to safely avoid near-miss events.

METHOD

Forty-eight licensed drivers using ADS were randomly assigned to either the active driving or passive driving condition. Participants navigated eight scenarios with or without a visual obstruction in a distributed driving simulator. The experimenter drove the other simulated vehicle to manually cause near-miss events. Participants' mean longitudinal velocity, standard deviation of longitudinal velocity, and mean longitudinal acceleration were measured.

RESULTS

Participants in passive ADS group showed greater, and more variable, deceleration rates than those in the active ADS group. Despite a reliable audiovisual warning, participants failed to slow down in the red-light running scenario when the conflict vehicle was occluded. Participant's trust in the automated driving system did not vary between the beginning and end of the experiment.

CONCLUSION

Drivers interacting with ADS in a passive manner may continue to show increased and more variable deceleration rates in near-miss scenarios even with reliable connected vehicle technology. Future research may focus on interactive effects of automated and connected driving technologies on drivers' ability to anticipate and safely navigate near-miss scenarios.

APPLICATION

Designers of automated and connected vehicle technologies may consider different timing and types of cues to inform the drivers of imminent hazard in high-risk scenarios for near-miss events.

Augmenting home entertainment with digitally delivered touch

In this narrative review, we take a critical look at the various attempts that have been made to augment home (or personal) entertainment experiences via the addition of some form of digitally controlled tactile stimulation. There has been an explosive growth in the market for home entertainment in recent years, and a majority of smartphones and other wearable electronic devices are now touch-enabled. As such, it is important to consider the challenges and potential opportunities for enhanced multisensory entertainment that may result from the introduction of tactile/haptic stimulation in the context of audiovisual digital storytelling and/or gaming. The key technological, financial (and legal), cognitive, and creative/artistic, challenges associated with the tactile augmentation of home entertainment experiences are outlined. Tactile augmentation, in the sphere of both public and personal entertainment, is more likely to succeed when it goes beyond the merely pleonastic vibrotactile reproduction of those interactions/events than can already be seen and/or heard on screen. At the same time, however, it remains uncertain under what conditions immersion in an entertainment experience will be enhanced by the addition of some form of primitive digital tactile stimulation. Ultimately, until a clear usage case can be made for the benefits of introducing a tactile element to home entertainment, it is unlikely to gain traction and switch from being merely a gimmick to more of a valuable element of multisensory storytelling.

Effects of collision warning characteristics on driving behaviors and safety in connected vehicle environments

With the emerging connected vehicle (CV) technologies, a novel in-vehicle omni-direction collision warning system (OCWS) is developed. For example, vehicles approaching from different directions can be detected, and advanced collision warnings caused by vehicles approaching from different directions can be provided. Effectiveness of OCWS in reducing crash and injury related to forward, rear-end and lateral collision is recognized. However, it is rare that the effects of collision warning characteristics including collision types and warning types on micro-level driver behaviors and safety performance is assessed. In this study, variations in drivers' responses among different collision types and between visual only and visual plus auditory warnings are examined. In addition, moderating effects by driver characteristics including drivers' demographics, years of driving experience, and annual driving distance are also considered. An in-vehicle human-machine interface (HMI) that can provide both visual and auditory warnings for forward, rear-end, and lateral collisions is installed on an instrumented vehicle. 51 drivers participate in the field tests. Performance indicators including relative speed change, time taken to accelerate/decelerate, and maximum lateral displacement are adopted to reflect drivers' responses to collision warnings. Then, generalized estimation equation (GEE) approach is applied to examine the effects of drivers' characteristics, collision type, warning type and their interaction on the driving performance. Results indicate that age, year of driving experience, collision type, and warning type can affect the driving performance. Findings should be indicative to the optimal design of in-vehicle HMI and thresholds for the activation of collision warnings that can increase the drivers' awareness to collision warnings from different directions. Also, implementation of HMI can be customized with respect to individual driver characteristics.

Multisensory alarm to benefit alarm identification and decrease workload: a feasibility study

The poor design of conventional auditory medical alarms has contributed to alarm desensitization, and eventually, alarm fatigue in medical personnel. This study tested a novel multisensory alarm system which aims to help medical personnel better interpret and respond to alarm annunciation during periods of high cognitive load such as those found within intensive care units. We tested a multisensory alarm that combined auditory and vibrotactile cues to convey alarm type, alarm priority, and patient identity. Testing was done in three phases: control (conventional auditory), Half (limited multisensory alarm), and Full (complete multisensory alarm). Participants (N = 19, undergraduates) identified alarm type, priority, and patient identity (patient 1 or 2) using conventional and multisensory alarms, while simultaneously completing a cognitively demanding task. Performance was based on reaction time (RT) and identification accuracy of alarm type and priority. Participants also reported their perceived workload. RT was significantly faster for the Control phase (p < 0.05). Participant performance in identifying alarm type, priority, and patient did not differ significantly between the three phase conditions (p = 0.87, 0.37, and 0.14 respectively). The Half multisensory phase produced the lowest mental demand, temporal demand, and overall perceived workload score. These data suggest that implementation of a multisensory alarm with alarm and patient information may decrease perceived workload without significant changes in alarm identification performance. Additionally, a ceiling effect may exist for multisensory stimuli, with only part of an alarm benefitting from multisensory integration.

When to use vibrotactile displays? A meta-analysis for the role of vibrotactile displays in human-computer interaction

OBJECTIVE

This study aims to investigate the benefits of unimodal tactile displays relative to other modal displays and the performance gains of adding redundant tactile displays by integrating empirical studies.

BACKGROUND

Tactile displays have attracted increasing attention in recent years due to their unique advantages. Synthesizing experimental data is necessary to analyze the performance benefits of tactile displays for participants and better help practitioners in utilizing them.

METHOD

Five meta-analyses were conducted. Two meta-analyses compared the participants' performance between tactile and other modal displays (visual vs. tactile and auditory vs. tactile). Three meta-analyses examined the performance gains of adding redundant tactile displays based on other modal displays (visual vs. visual + tactile, auditory vs. auditory + tactile, and visual + auditory vs. visual + auditory + tactile). The related moderator variables, the types of presented information and concurrent tasks, were analyzed.

RESULTS

Little evidence shows the performance difference between tactile and auditory displays. Tactile displays are more beneficial than visual displays for presenting alert information or in the situation with a visual concurrent task. The performance gains of adding redundant tactile displays to other modal displays also depend on the specific type of presented information and the concurrent task.

CONCLUSION

When using tactile displays to convey information, interface designers should consider the specific type of presented information and the concurrent tasks.

APPLICATIONS

The present study's findings can provide some implications for designers to utilize tactile displays when they construct and implement information displays.

Digital haptics improve speed of visual search performance in a dual-task setting

Dashboard-mounted touchscreen tablets are now common in vehicles. Screen/phone use in cars likely shifts drivers’ attention away from the road and contributes to risk of accidents. Nevertheless, vision is subject to multisensory influences from other senses. Haptics may help maintain or even increase visual attention to the road, while still allowing for reliable dashboard control. Here, we provide a proof-of-concept for the effectiveness of digital haptic technologies (hereafter digital haptics), which use ultrasonic vibrations on a tablet screen to render haptic perceptions. Healthy human participants (N = 25) completed a divided-attention paradigm. The primary task was a centrally-presented visual conjunction search task, and the secondary task entailed control of laterally-presented sliders on the tablet. Sliders were presented visually, haptically, or visuo-haptically and were vertical, horizontal or circular. We reasoned that the primary task would be performed best when the secondary task was haptic-only. Reaction times (RTs) on the visual search task were fastest when the tablet task was haptic-only. This was not due to a speed-accuracy trade-off; there was no evidence for modulation of VST accuracy according to modality of the tablet task. These results provide the first quantitative support for introducing digital haptics into vehicle and similar contexts.

Effect of mapping characteristic on audiovisual warning: Evidence from a simulated driving study

Advanced driver assistance systems (ADAS) can enhance road safety by sending warning signals to drivers. Multimodal signals are gaining attention in ADAS warning design because they offer redundant information that facilitates human-system communication. However, no consensus has been reached on which multimodal design offers optimal benefit to road safety. Icons iconically map the real world and are associated with fast recognition and response time. Therefore, this study aims to investigate whether visual and auditory icons will benefit the effectiveness of audiovisual multimodal warnings. Thirty-two participants (16 females) experienced four types of unimodal warnings (high and low mapping visual warnings and high and low mapping auditory warnings) and four types of audiovisual warnings (high mapping visual + high mapping auditory warning, low mapping visual + low mapping auditory warning, high mapping visual + low mapping auditory warning, and low mapping visual + high mapping auditory warning) in simulated driving conditions. Visual warnings are presented in a head-up display. Results showed that multimodal warnings outperformed unimodal warnings (i.e., modality effect). We found mapping effect in audiovisual warnings, but only high mapping auditory constituents benefited warning effectiveness. Eye movement results revealed that the high mapping constituents might distract drivers from the road. This study adds evidence that multimodal warnings can offer extra benefits to drivers and high mapping auditory signals should be included in multimodal warning design to achieve better driving performance.

A Comparison of Vibrotactile Feedback and Electrical Muscle Stimulation (EMS) for Motor Response During Active Hand Movement

Wearable haptic technologies have garnered recent widespread attention due to increased accessibility, functionality, and affordability. These systems typically provide haptic feedback to augment the human ability to interact with their environment. This study compares two haptic feedback modalities, vibrotactile and EMS, against visual feedback to elicit a motor response during active hand movement. Forty-five participants, divided into three groups, performed a task to touch their face and received one of three possible sensory feedback cues, namely visual, vibrotactile, and electrical muscle stimulation (EMS), to interrupt their movement and avoid touching their face. Two quantitative performance measures are used in the comparison, the response time (time elapsed from stimulation to motor response) and the error rate (percentage that the user fails to avoid touching their face). Results showed that vibrotactile and EMS feedback yielded significantly faster response time than visual feedback, while no significant differences between vibrotactile and EMS were observed. Furthermore, the error rate was significantly lower for EMS compared to visual feedback, whereas no significant differences were observed between vibrotactile and visual feedback. In conclusion, it seems that EMS feedback is preferable for applications where errors are not tolerable (critical medical applications), whereas vibrotactile is superior for non-critical applications due to its low cost and higher usability (more pleasant compared to EMS).

Impact Vibration Source Localization in Two-Dimensional Space Around Hand

This article investigated the localization ability of an impulse vibration source outside the body in two-dimensional space. We tested whether humans can recognize the direction or distance of an impulse vibration source when using their hand to detect spatiotemporal vibrotactile information provided by the propagated vibrational wave from the source. Specifically, we had users put their hands on a silicone rubber sheet in several postures. We asked users to indicate the position of the vibration source when a location on the sheet was indented. Experimental results suggested that the direction of the impact vibration source can be recognized to some extent, although recognition accuracy depends on hand posture and the position of the vibration source. The best results were achieved when the fingers and palm were grounded and a vibration source was presented around the middle fingertip, and the directional recognition error in this case was 6 ^°. In contrast, results suggest it is difficult to accurately recognize the distance of the vibration. The results of this study suggest a new possibility for directional display where vibrotactile actuators are embedded at a distance from the user's hand.

A Sensaptic ADAS Device Using Shape Memory Alloy Wires: Design and Control

This paper presents an active accelerator pedal system based on an integrated sensor and actuator using shape memory alloy (SMA) for speed control and to create haptics in the accelerator pedal. A device named sensaptics is developed with a pair of bi-functional SMA wires instrumented in a synergistic configuration function as an active sensor for positioning the accelerator pedal (pedal position sensing) to control the vehicle speed through electronic throttle and as a variable impedance actuator to generate active force (haptic) feedback to the driver. The reaction force emanated from the pedal alerts the driver and takes appropriate control action by slowing down the vehicle, in harmony with the road’s condition. The design is developed as a proof-of-concept device and is tested and evaluated in a real-time common rail diesel system for rail pressure regulation and over speeding tests, and the responses and performances are found to be promising.

Auditory stimuli degrade visual performance in virtual reality

We report an auditory effect of visual performance degradation in a virtual reality (VR) setting, where the viewing conditions are significantly different from previous studies. With the presentation of temporally congruent but spatially incongruent sound, we can degrade visual performance significantly at detection and recognition levels. We further show that this effect is robust to different types and locations of both auditory and visual stimuli. We also analyze participants behavior with an eye tracker to study the underlying cause of the degradation effect. We find that the performance degradation occurs even in the absence of saccades towards the sound source, during normal gaze behavior. This suggests that this effect is not caused by oculomotor phenomena, but rather by neural interactions or attentional shifts.

Feeling Uncertain—Effects of a Vibrotactile Belt that Communicates Vehicle Sensor Uncertainty

With the rise of partially automated cars, drivers are more and more required to judge the degree of responsibility that can be delegated to vehicle assistant systems. This can be supported by utilizing interfaces that intuitively convey real-time reliabilities of system functions such as environment sensing. We designed a vibrotactile interface that communicates spatiotemporal information about surrounding vehicles and encodes a representation of spatial uncertainty in a novel way. We evaluated this interface in a driving simulator experiment with high and low levels of human and machine confidence respectively caused by simulated degraded vehicle sensor precision and limited human visibility range. Thereby we were interested in whether drivers (i) could perceive and understand the vibrotactile encoding of spatial uncertainty, (ii) would subjectively benefit from the encoded information, (iii) would be disturbed in cases of information redundancy, and (iv) would gain objective safety benefits from the encoded information. To measure subjective understanding and benefit, a custom questionnaire, Van der Laan acceptance ratings and NASA TLX scores were used. To measure the objective benefit, we computed the minimum time-to-contact as a measure of safety and gaze distributions as an indicator for attention guidance. Results indicate that participants were able to understand the encoded uncertainty and spatiotemporal information and purposefully utilized it when needed. The tactile interface provided meaningful support despite sensory restrictions. By encoding spatial uncertainties, it successfully extended the operating range of the assistance system.

Combination of Simultaneous Artificial Sensory Percepts to Identify Prosthetic Hand Postures: A Case Study

Multiple sources of sensory information are combined to develop hand posture percepts in the intact system, but the combination of multiple artificial somatosensory percepts by human prosthesis users has not been studied. Here, we report on a case study in which a person with transradial amputation identified prosthetic hand postures using artificial somatosensory feedback. He successfully combined five artificial somatosensory percepts to achieve above-chance performance of 95.0% and 75.7% in identifying four and seven postures, respectively. We studied how artificial somatosensation and the extant hand representation are combined in the decision-making process by providing two mappings between the prosthetic sensor and the location of the sensory percept: (1) congruent, and (2) incongruent. The participant's ability to combine and engage with the sensory feedback significantly differed between the two conditions. The participant was only able to successfully generalize prior knowledge to novel postures in the congruent mapping. Further, he learned postures more accurately and quickly in the congruent mapping. Finally, he developed an understanding of the relationships between postures in the congruent mapping instead of simply memorizing each individual posture. These experimental results are corroborated by a Bayesian decision-making model which tracked the participant's learning.

Effect of Auditory Feedback on Tactile Intensity Perception in a Touchscreen Application

This article presents the effect of auditory feedback on tactile intensity perception, which may be of interest to haptic or audiotactile interaction engineers. An experimental setup consisted of a touchscreen, an electrodynamic shaker, and a closed-back headphone for a subject to interact with the touchscreen and to feel audiotactile feedback. In the experiment, participants were asked to judge perceived tactile intensity, using the magnitude estimation method, in the absence and presence of simultaneous auditory feedback. All data collected from the subjects were analyzed statistically, and then the effect of auditory feedback was investigated focusing on the following aspects: whether the presence of auditory feedback changes perceived tactile intensity, whether the frequency component of auditory feedback affects tactile intensity perception, and whether the coincidence of tactile and auditory frequencies influences on tactile intensity perception. Besides, changes in Stevens's exponent were analyzed to discuss how tactile intensity perception varies due to the auditory feedback. Finally, an equal intensity contour, in the domain of sensation level and frequency of tactile stimulation, was drawn. It can be applied to adjust the level of tactile stimuli for haptic feedback designers to provide a constant perceived tactile intensity considering the presence of auditory feedback.

Advanced driver assistance systems: Using multimodal redundant warnings to enhance road safety

This study investigated whether multimodal redundant warnings presented by advanced assistance systems reduce brake response times. Warnings presented by assistance systems are designed to assist drivers by informing them that evasive driving maneuvers are needed in order to avoid a potential accident. If these warnings are poorly designed, they may distract drivers, slow their responses, and reduce road safety. In two experiments, participants drove a simulated vehicle equipped with a forward collision avoidance system. Auditory, vibrotactile, and multimodal warnings were presented when the time to collision was shorter than five seconds. The effects of these warnings were investigated with participants performing a concurrent cell phone conversation (Exp. 1) or driving in high-density traffic (Exp. 2). Braking times and subjective workload were measured. Multimodal redundant warnings elicited faster braking reaction times. These warnings were found to be effective even when talking on a cell phone (Exp. 1) or driving in dense traffic (Exp. 2). Multimodal warnings produced higher ratings of urgency, but ratings of frustration did not increase compared to other warnings. Findings obtained in these two experiments are important given that faster braking responses may reduce the potential for a collision.

The Effect of Haptic Support Systems on Driver Performance: A Literature Survey

A large number of haptic driver support systems have been described in the scientific literature. However, there is little consensus regarding the design, evaluation methods, and effectiveness of these systems. This literature survey aimed to investigate: (1) what haptic systems (in terms of function, haptic signal, channel, and supported task) have been experimentally tested, (2) how these haptic systems have been evaluated, and (3) their reported effects on driver performance and behaviour. We reviewed empirical research in which participants had to drive a vehicle in a real or simulated environment, were able to control the heading and/or speed of the vehicle, and a haptic signal was provided to them. The results indicated that a clear distinction can be made between warning systems (using vibrations) and guidance systems (using continuous forces). Studies typically used reaction time measures for evaluating warning systems and vehicle-centred performance measures for evaluating guidance systems. In general, haptic warning systems reduced the reaction time of a driver compared to no warnings, although these systems may cause annoyance. Guidance systems generally improved the performance of drivers compared to non-aided driving, but these systems may suffer from after-effects. Longitudinal research is needed to investigate the transfer and retention of effects caused by haptic support systems.

Irrelevant tactile stimulation biases visual exploration in external coordinates

We evaluated the effect of irrelevant tactile stimulation on humans’ free-viewing behavior during the exploration of complex static scenes. Specifically, we address the questions of (1) whether task-irrelevant tactile stimulation presented to subjects’ hands can guide visual selection during free viewing; (2) whether tactile stimulation can modulate visual exploratory biases that are independent of image content and task goals; and (3) in which reference frame these effects occur. Tactile stimulation to uncrossed and crossed hands during the viewing of static images resulted in long-lasting modulation of visual orienting responses. Subjects showed a well-known leftward bias during the early exploration of images, and this bias was modulated by tactile stimulation presented at image onset. Tactile stimulation, both at image onset and later during the trials, biased visual orienting toward the space ipsilateral to the stimulated hand, both in uncrossed and crossed hand postures. The long-lasting temporal and global spatial profile of the modulation of free viewing exploration by touch indicates that cross-modal cues produce orienting responses, which are coded exclusively in an external reference frame.

Dynamic vibrotactile signals for forward collision avoidance warning systems

OBJECTIVE

Four experiments were conducted in order to assess the effectiveness of dynamic vibrotactile collision-warning signals in potentially enhancing safe driving.

BACKGROUND

Auditory neuroscience research has demonstrated that auditory signals that move toward a person are more salient than those that move away. If this looming effect were found to extend to the tactile modality, then it could be utilized in the context of in-car warning signal design.

METHOD

The effectiveness of various vibrotactile warning signals was assessed using a simulated car-following task. The vibrotactile warning signals consisted of dynamic toward-/away-from-torso cues (Experiment 1), dynamic versus static vibrotactile cues (Experiment 2), looming-intensity- and constant-intensity-toward-torso cues (Experiment 3), and static cues presented on the hands or on the waist, having either a low or high vibration intensity (Experiment 4).

RESULTS

Braking reaction times (BRTs) were significantly faster for toward-torso as compared to away-from-torso cues (Experiments 1 and 2) and static cues (Experiment 2). This difference could not have been attributed to differential responses to signals delivered to different body parts (i.e., the waist vs. hands; Experiment 4). Embedding a looming-intensity signal into the toward-torso signal did not result in any additional BRT benefits (Experiment 3).

CONCLUSION

Dynamic vibrotactile cues that feel as though they are approaching the torso can be used to communicate information concerning external events, resulting in a significantly faster reaction time to potential collisions.

APPLICATION

Dynamic vibrotactile warning signals that move toward the body offer great potential for the design of future in-car collision-warning system.

Tactile warning signals for in-vehicle systems

The last few years have seen growing interest in the design of tactile warning signals to direct driver attention to potentially dangerous road situations (e.g. an impending crash) so that they can initiate an avoidance maneuver in a timely manner. In this review, we highlight the potential uses of such warning signals for future collision warning systems and compare them with more traditional visual and auditory warnings. Basic tactile warning signals are capable of promoting driver alertness, which has been demonstrated to be beneficial for forward collision avoidance (when compared to a no warning baseline condition). However, beyond their basic alerting function, directional tactile warning signals are now increasingly being utilized to shift the attention of the driver toward locations of interest, and thus to further facilitate their speeded responses to potential collision events. Currently, many researchers are focusing their efforts on the development of meaningful (iconic) tactile warning signals. For instance, dynamic tactile warnings (varying in their intensity and/or location) can potentially be used to convey meaningful information to drivers. Finally, we highlight the future research that will be needed in order to explore how to present multiple directional warnings using dynamic tactile cues, thus forming an integrated collision avoidance system for future in-vehicle use.

Dynamic vibrotactile warning signals for frontal collision avoidance: towards the torso versus towards the head

Three experiments were conducted to assess the effectiveness of dynamic vibrotactile warning signals with different spatial patterns and to compare dynamic towards-torso and towards-head vibrotactile warnings in a simulated driving task. The results revealed that embedding additional stimuli between the participant's hands and waist in the towards-torso cues (Experiment 1) and increasing the spatial distance between adjacent stimuli in the towards-head cues (Experiment 2) did not result in any further benefits in braking response times (BRTs). The triple towards-head cues resulting from the sequential operation of three pairs of stimuli on the torso gave rise to a significant advantage over the static cues; however, it did not outperform the dynamic towards-torso cues with just two pairs of stimuli. Taken together, these results demonstrated the promise of dynamic vibrotactile warnings (especially, the towards-torso warnings) in terms of the future design of more effective rear-end collision warnings.

PRACTITIONER SUMMARY

Three experiments assessed the effectiveness of dynamic towards-torso and towards-head vibrotactile warning signals in a simulated driving task. The results demonstrated the promise of dynamic vibrotactile warnings (especially, the towards-torso vibrotactile warnings) in terms of the future design of more effective frontal collision warnings.

Tactile stimulations and wheel rotation responses: toward augmented lane departure warning systems

When an on-board system detects a drift of a vehicle to the left or to the right, in what way should the information be delivered to the driver? Car manufacturers have so far neglected relevant results from Experimental Psychology and Cognitive Neuroscience. Here we show that this situation possibly led to the sub-optimal design of a lane departure warning system (AFIL, PSA Peugeot Citroën) implemented in commercially available automobile vehicles. Twenty participants performed a two-choice reaction time task in which they were to respond by clockwise or counter-clockwise wheel-rotations to tactile stimulations of their left or right wrist. They performed poorer when responding counter-clockwise to the right vibration and clockwise to the left vibration (incompatible mapping) than when responding according to the reverse (compatible) mapping. This suggests that AFIL implements the worse (incompatible) mapping for the operators. This effect depended on initial practice with the interface. The present research illustrates how basic approaches in Cognitive Science may benefit to Human Factors Engineering and ultimately improve man-machine interfaces and show how initial learning can affect interference effects.

Enhanced perception and performance by multimodal threat cueing in simulated combat vehicle

OBJECTIVE

In a simulated combat vehicle, uni-, bi-, and trimodal cueing of direction to threat were compared with the purpose to investigate whether multisensory redundant information may enhance dynamic perception and performance.

BACKGROUND

Previous research has shown that multimodal display presentation can enhance perception of information and task performance.

METHOD

Two experiments in a simulated combat vehicle were performed under the instructions to turn the vehicle toward the threat as fast and accurately as possible after threat cue onset. In Experiment 1, direction to threat was presented by four display types: visual head-down display, tactile belt, 3-D audio, and trimodal with the three displays combined. In Experiment 2, direction to threat was presented by three display types: visual head-up display (HUD)-3-D audio, tactile belt-3-D audio, and trimodal with HUD, tactile belt, and 3-D audio combined.

RESULTS

In Experiment I,the trimodal display provided overall best performance and perception of threat direction. In Experiment 2, both the trimodal and HUD--3-D audio displays led to overall best performance, and the trimodal display provided overall the best perception of threat direction. None of the trimodal displays induced higher mental workload or secondary task interference.

CONCLUSION

The trimodal displays provided overall enhanced perception and performance in the dynamically framed threat scenario and did not entail higher mental workload or decreased spare capacity.

APPLICATION

Trimodal displays with redundant information may contribute to safer and more reliable peak performance in time-critical dynamic tasks and especially in more extreme and stressful situations with high perceptual or mental workload.

Vibrotactile Feedback for Information Delivery in the Vehicle

As technology advances, more functions have been, and continue to be added to the vehicle, resulting in increased needs for improved user interfaces. In this paper, we investigate the feasibility of using vibrotactile feedback for in-vehicle information delivery. First, we measured the spectral characteristics of ambient vibrations in a vehicle, and designed clearly distinguishable sinusoidal vibrations. We further selected via dissimilarity rating the four sets of sinusoidal vibrations which had three to six vibrations. Second, we evaluated the learnability of the vibration sets when associated with common menu items of a Driver Information System (DIS). We also replaced the two most confused sinusoidal vibrations with patterned messages, and assessed the degree of learnability improvement. Finally, we evaluated the extent to which participants could select a desired function in a DIS via vibrotactile messages while simultaneously performing a driving-like primary task with higher priority. The results demonstrated high potential for vibrotactile messages to be effectively used for the communicative transfer of in-vehicle system information.

Using peripersonal warning signals to orient a driver's gaze

OBJECTIVE

We report a series of three experiments designed to assess the relative speed with which people can initiate speeded head-orienting responses following the presentation of spatial warning signals.

BACKGROUND

Recent cognitive neuroscience findings have shown that the human brain tends to treat stimuli occurring in peripersonal space as being somehow more behaviorally relevant and attention demanding than stimuli occurring in extrapersonal space. These brain mechanisms may be exploited in the design of warning signals.

METHOD

Experiment 1 assessed the effectiveness of various different unisensory warning signals in eliciting a head-turning response to look at the potential source of danger requiring participants' immediate attention; Experiment 2 assessed the latency of a driver's responses to events occurring in the cued direction; Experiment 3 assessed the relative effectiveness of various warning signals in reorienting a person's gaze back to a central driving task while he or she was distracted by a secondary task.

RESULTS

The results show that participants initiated head-turning movements and made speeded discrimination or braking responses significantly more rapidly following the presentation of a close rear auditory warning signal than following the presentation of either a far frontal auditory warning signal, a vibrotactile warning signal presented to their waist, or a peripheral visual warning signal.

CONCLUSION

These results support the claim that the introduction of peripersonal warning signals results in a significant performance advantage relative to traditionally designed warnings.

APPLICATION

Warning systems that have been designed around the constraints of the human brain offer great potential in the future design ofmultisensory interfaces.

Capturing spatial attention with multisensory cues: a review

The last 30 years have seen numerous studies demonstrating unimodal and crossmodal spatial cuing effects. However, surprisingly few studies have attempted to investigate whether multisensory cues might be any more effective in capturing a person's spatial attention than unimodal cues. Indeed, until very recently, the consensus view was that multisensory cues were, in fact, no more effective. However, the results of several recent studies have overturned this conclusion, by showing that multisensory cues retain their attention-capturing ability under conditions of perceptual load (i.e., when participants are simultaneously engaged in a concurrent attention-demanding task) while their constituent signals (when presented unimodally) do not. Here we review the empirical literature on multisensory spatial cuing effects and highlight the implications that this research has for the design of more effective warning signals in applied settings.

Tactile and Multisensory Spatial Warning Signals for Drivers

The last few years have seen many exciting developments in the area of tactile and multisensory interface design. One of the most rapidly-moving practical application areas for these findings is in the development of warning signals and information displays for drivers. For instance, tactile displays can be used to awaken sleepy drivers, to capture the attention of distracted drivers, and even to present more complex information to drivers who may be visually-overloaded. This review highlights the most important potential costs and benefits associated with the use of tactile and multisensory information displays in a vehicular setting. Multisensory displays that are based on the latest cognitive neuroscience research findings can capture driver attention significantly more effective than their unimodal (i.e., tactile) counterparts. Multisensory displays can also be used to transmit information more efficiently, as well as to reduce driver workload. Finally, we highlight the key research questions currently awaiting further research, including questions such as: Are tactile warning signals really intuitive? Are there certain regions of the body (or in the space surrounding the body) where tactile/multisensory warning signals are particularly effective? To what extent is the spatial coincidence and temporal synchrony of the individual sensory signals critical to determining the effectiveness of multisensory displays? And, finally, how does the issue of compliance vs. reliance (or the 'cry wolf' phenomenon associated with the presentation of signals that are perceived as false alarms) influence the effectiveness of tactile and/or multisensory warning signals?