The utility of telematics data for estimating the prevalence of driver handheld cellphone use, 2019-2022.

INTRODUCTION: Driver distraction from handheld cellphone use contributes to fatal crashes every year but is underreported in terms of the proportion of crashes attributed to any distraction or cellphone use specifically. Existing methods to estimate the prevalence of cellphone distractions are also limited (e.g., observing drivers stopped at intersections, when crash risk is low). Our study used data from Cambridge Mobile Telematics to estimate the prevalence of drivers' handheld calls and cellphone manipulation while driving, with "cellphone motion" based on movement recorded by the phones' gyroscopes used as a surrogate for manipulation. METHOD: We compared the telematics measures with the National Highway Traffic Safety Administration's roadside observations of driver electronic device use, and logistic regression tested relationships between regional, legislative, and temporal factors and the odds of cellphone behaviors occurring on a trip or at a given point in time. RESULTS: Results showed 3.5% of trips included at least one handheld phone call and 33.3% included at least an instance of cellphone motion, with handheld calls occurring during 0.78% of overall trip duration and cellphone motion during 2.4% of trip duration. CONCLUSIONS: Correspondence between trends in cellphone distractions across regional, legislative, and temporal factors suggest telematics data have considerable utility and appear to complement existing datasets.

The association between strengthened cellphone laws and police-reported rear-end crash rates.

INTRODUCTION: Prior evaluations of the connection between cellphone bans and crashes show unclear results. California, Oregon, and Washington enacted legislation (effective in 2017) to update earlier bans specific to handheld conversation and texting. This study evaluated the relationship between the laws and rear-end rates, a crash type sensitive to visual-manual cellphone use, in California, Oregon, and Washington. METHOD: Negative binomial regression compared the change in monthly per capita rear-end crash rates in California, Oregon, and Washington before and after the law changes relative to two control states, Colorado and Idaho, during 2015-2019. Analyses examined (a) rear-end crashes with injuries in all three study states, including minor to fatal injuries; and (b) rear-end crashes of all severities in California and Washington, including property-damage-only crashes and crashes with injuries; Oregon was excluded from this analysis because of a 2018 change to its reporting criteria for property-damage-only crashes. RESULTS: Washington's strengthened law was associated with a significant 7.6% reduction in the rate of monthly rear-end crashes of all severities relative to the controls. Law changes in Oregon and Washington were associated with significant reductions of 8.8% and 10.9%, respectively, in the rates of monthly rear-end crashes with injury relative to the controls. California did not experience changes in rear-end crash rates of all severities or with injuries associated with the strengthened law. CONCLUSION: The results of this study are mixed, with law changes associated with significant reductions in rear-end crash rates in two of the three study states. Differences in the wording of the laws, levels of enforcement, and sanction severity may help explain the divergent results. PRACTICAL APPLICATION: Crash reductions in Oregon and Washington suggest that enacting legislation that comprehensively bans practically all visual-manual cellphone activity may have made the laws easier to enforce and clarified to drivers that handheld cellphone use is unacceptable in these states.

Prevalence of distracted driving by driver characteristics in the United States.

INTRODUCTION: Distracted driving is a long-standing traffic safety concern, though common secondary tasks continually evolve. The goal of this study was to measure the prevalence of self-reported distracted driving behaviors, including activities made possible in recent years by smartphones. METHODS: We conducted a nationwide survey of 2,013 U.S. licensed drivers (ages 16 +). We created four aggregate distraction categories from 18 individual secondary tasks to estimate the proportion of drivers study-wide and by demographic characteristics belonging to each category, defined as those who regularly did (during most or all drives in the previous 30 days) one or more secondary task within each category. Logistic regression estimated the adjusted odds of drivers belonging to each aggregate distraction category by demographic characteristics. RESULTS: Sixty-five percent of drivers reported doing at least one of the 18 secondary tasks regularly, and half did at least one device-based task regularly in the past 30 days. Non-device task prevalence trended downward with age, while device-based task prevalence was consistent among younger drivers before declining beginning with age 35. Males (OR, 1.53; 95% CI, 1.16, 2.02), parents of children ages 18 and younger (OR, 1.47; 95% CI, 1.10, 1.96), and participants who drive in the gig economy (OR, 3.85; 95% CI, 2.73, 5.43) had higher adjusted odds of engaging in "modern" device-based distractions enabled by smartphones (e.g., making video calls, watching videos, using social media) than other drivers. Many drivers are using hands-free capabilities when available for tasks, but for some tasks more than others. CONCLUSIONS: Regular distracted driving is widespread with most behavior concentrated among drivers younger than age 50, though no age group or other demographic studied abstains. PRACTICAL APPLICATIONS: Stakeholders can use these findings to develop countermeasures for distracted driving by targeting specific secondary tasks and the demographics most likely to report regularly doing them.

Speeding behavior while using adaptive cruise control and lane centering in free flow traffic.

OBJECTIVE: Adaptive cruise control (ACC) and lane centering are usually marketed as convenience features but may also serve a safety purpose. However, given that speeding is associated with increased crash risk and worse crash outcomes, the extent to which driver's speed using ACC may reduce the maximum safety benefit they can obtain from this system. The current study was conducted to characterize speeding behavior among drivers using adaptive cruise control and a similar system with added lane centering. METHODS: We recruited 40 licensed adult drivers from the Boston, Massachusetts, metro area. These drivers were given either a 2017 Volvo S90 or a 2016 Range Rover Evoque to use for about 4 weeks. RESULTS: Drivers were significantly more likely to speed while they used ACC (95%) relative to periods of manual control (77%). A similar pattern arose for drivers using ACC with added lane centering (96% vs. 77%). Drivers who traveled over the posted limit with these systems engaged also sped slightly faster than drivers controlling their vehicle manually. Finally, we found that these differences were the most pronounced on limited-access roads with a lower speed limit (55 mph). CONCLUSIONS: These findings point to a possible obstacle to obtaining the full safety potential from this advanced vehicle technology. Any consideration of the net safety effect of ACC and lane centering should account for the effects of more frequent and elevated speeding.

Patterns in transitions of visual attention during baseline driving and during interaction with visual-manual and voice-based interfaces.

Voice interfaces reduce visual demand compared with visual-manual interfaces, but the extent depends on design. This study compared visual demand during baseline driving with driving while using voice or manual inputs to place calls with Chevrolet MyLink, Volvo Sensus, or a smartphone. Mean glance duration and total eyes-off-road-time increased when using manual input compared with baseline driving; only eyes off road time increased with voice input. Confusion matrices developed with hidden Markov modelling characterise the similarity of glance sequences during baseline driving and while making phone calls. Glance sequences with the MyLink voice interface were misclassified as baseline driving more frequently than the other voice interfaces. Conversely, glance sequences with the Sensus and smartphone voice interfaces were more often misclassified as manual phone calling. Thus, the MyLink voice interface not only reduced the overall visual demand of placing calls, but produced glance patterns more similar to driving without another task. Practitioner Summary: The attention map and confusion matrix methodologies provide ways of characterising similarities and differences in glance behaviour across secondary task conditions, complementing traditional temporally based metrics (e.g. mean glance duration, long duration glances) while addressing some of the limitations of total-eyes-off-road-time (TEORT) for comparing secondary task behaviour to baseline driving.

Exploring relationships between observed activation rates and functional attributes of lane departure prevention.

Objective: Drivers' use of lane departure warning and prevention systems is lower than use of other crash avoidance technologies and varies significantly by manufacturer. One factor that may affect use is how well a system prevents unintended departures. The current study evaluated the performance of systems that assist in preventing departures by providing steering or braking input in a 2016 Chevrolet Malibu, 2016 Ford Fusion, 2016 Honda Accord, and 2018 Volvo S90. These vehicles were selected because a prior observational study found that the percentage of privately owned vehicles that had lane departure prevention systems turned on varied among these 4 automakers. Method: In each vehicle, a test driver induced 40 lane drifts on left and right curves by steering the vehicle straight into the curve so that vehicles departed in the opposite direction and 40 lane drifts on straightaways by slight steering input to direct the vehicle to left and right lane markers. Results: Vehicles from automakers with higher observed lane departure prevention use rates (Volvo, Chevrolet) featured systems that provided steering input earlier and more often avoided crossing lane markers by more than 35 cm compared to vehicles from automakers with lower observed use rates (Ford, Honda). Conclusion: The study identified functional characteristics (i.e., timing of steering input, prevention of departures more than 35 cm) of lane departure prevention systems that were strongly associated with observed activation of these systems in privately owned vehicles. Although this relationship does not imply causation, the findings support the hypothesis that functional characteristics of lane departure prevention systems affect their use. Designers may be able to use these results to maximize driver acceptance of future implementations of lane departure prevention.

High beam headlamp use rates: Effects of rurality, proximity of other traffic, and roadway curvature.

OBJECTIVE: The few observational studies of the prevalence of high beam use indicate the rate of high beam use is about 25% when vehicles are isolated from other vehicles on unlit roads. Recent studies were limited to 2-lane rural roads and used measurement methods that likely overestimated use. The current study examined factors associated with the rate of high beam use of isolated vehicles on a variety of roadways in the Ann Arbor, Michigan area. METHODS: Twenty observation sites were categorized as urban, rural, or on a rural/urban boundary and selected to estimate the effects of street lighting, road curvature, and direction of travel relative to the city on high beam use. Sites were selected in pairs so that a majority of traffic passing one site also passed through the other. Measurement of high beams relied on video data recorded for 2 nights at each site, and the video data also were used to derive a precise measure of the proximity of other traffic. Nearly 3,200 isolated vehicles (10 s or longer from other vehicles) were observed, representing 1,500-plus vehicle pairs. RESULTS: Across the sample, 18% of the vehicles used high beams. Seventy-three percent of the 1,500-plus vehicle pairs used low beams at each paired site, whereas 9% used high beams at both sites. Vehicles at rural sites and sites at the boundaries of Ann Arbor were more likely to use high beams than vehicles at urban sites, but use in rural areas compared with rural/urban boundary areas did not vary significantly. Rates at all sites were much lower than expected, ranging from 0.9 to 52.9%. High beam use generally increased with greater time between subject vehicles and leading vehicles and vehicles in the opposing lane. There were mixed findings associated with street lighting, road curvature, and direction of travel relative to the city. CONCLUSION: Maximizing visibility available to drivers from headlights includes addressing the substantial underuse of high beam headlamps. Advanced technologies such as high beam assist, which switches automatically between high and low beam headlamps depending on the presence of other traffic, can help to address this problem.

Driver trust in five driver assistance technologies following real-world use in four production vehicles.

OBJECTIVES: Information about drivers' experiences with driver assistance technologies in real driving conditions is sparse. This study characterized driver interactions with forward collision warning, adaptive cruise control, active lane keeping, side-view assist, and lane departure warning systems following real-world use. METHODS: Fifty-four Insurance Institute for Highway Safety employees participated and drove a 2016 Toyota Prius, 2016 Honda Civic, 2017 Audi Q7, or 2016 Infiniti QX60 for up to several weeks. Participants reported mileage and warnings from the technologies in an online daily-use survey. Participants reported their level of agreement with five statements regarding trust in an online post-use survey. Responses were averaged to create a composite measure of trust ranging from -2 (strongly disagree) to +2 (strongly agree) for each technology. Mixed-effect regression models were constructed to compare trust among technologies and separately among the study vehicles. Participants' free-response answers about what they liked least about each system were coded and examined. RESULTS: Participants reported driving 33,584 miles during 4 months of data collection. At least one forward collision warning was reported in 26% of the 354 daily reports. The proportion of daily reports indicating a forward collision warning was much larger for the Honda (70%) than for the Audi (18%), Infiniti (15%), and Toyota (10%). Trust was highest for side-view assist (0.98) and lowest for active lane keeping (0.20). Trust in side-view assist was significantly higher than trust in active lane keeping and lane departure warning (0.53). Trust in active lane keeping was significantly lower than trust in adaptive cruise control (0.67) and forward collision warning (0.71). Trust in adaptive cruise control was higher for the Audi (0.72) and Toyota (0.75) compared with the Honda (0.30), and significantly higher for the Infiniti (0.93). Trust in Infiniti's side-view assist (0.58) was significantly lower than trust in Audi (1.17) and Honda (1.23) systems. Coding of answers to free-response questions showed that more than 80% of complaints about Honda's adaptive cruise control were about the way it functioned and/or performed. Infiniti's side-view assist was the only one with complaints mentioning circumstances where it was used. Trust in forward collision warning, lane departure warning, and active lane keeping was not significantly different among vehicles. CONCLUSIONS: Driver trust varied among driver assistance technologies, and trust in adaptive cruise control and side-view assist differed among vehicles. Trust may affect real-world use of driver assistance technologies and limit the opportunity for the systems to provide their intended benefits.

Drivers' detection of roadside targets when driving vehicles with three headlight systems during high beam activation.

A previous open-road experiment indicated that curve-adaptive HID headlights driven with low beams improved drivers' detection of low conspicuity targets compared with fixed halogen and fixed HID low beam systems. The current study used the same test environment and targets to assess whether drivers' detection of targets was affected by the same three headlight systems when using high beams. Twenty drivers search and responded for 60 8×12inch targets of high or low reflectance that were distributed evenly across straight and curved road sections as they drove at 30 mph on an unlit two-lane rural road. The results indicate that target detection performance was generally similar across the three systems. However, one interaction indicated that drivers saw low reflectance targets on straight road sections from further away when driving with the fixed halogen high beam condition compared with curve-adaptive HID high beam headlights and also indicated a possible benefit for the curve-adaptive HID high beams for high reflectance targets placed on the inside of curves. The results of this study conflict with the previous study of low beams, which showed a consistent benefit for the curve-adaptive HID low beams for targets placed on curves compared with fixed HID and fixed halogen low beam conditions. However, a comparison of mean detection distances from the two studies indicated uniformly longer mean target detection distances for participants driving with high beams and implicates the potential visibility benefits for systems that optimize proper high beam use.

Multi-modal demands of a smartphone used to place calls and enter addresses during highway driving relative to two embedded systems.

There is limited research on trade-offs in demand between manual and voice interfaces of embedded and portable technologies. Mehler et al. identified differences in driving performance, visual engagement and workload between two contrasting embedded vehicle system designs (Chevrolet MyLink and Volvo Sensus). The current study extends this work by comparing these embedded systems with a smartphone (Samsung Galaxy S4). None of the voice interfaces eliminated visual demand. Relative to placing calls manually, both embedded voice interfaces resulted in less eyes-off-road time than the smartphone. Errors were most frequent when calling contacts using the smartphone. The smartphone and MyLink allowed addresses to be entered using compound voice commands resulting in shorter eyes-off-road time compared with the menu-based Sensus but with many more errors. Driving performance and physiological measures indicated increased demand when performing secondary tasks relative to 'just driving', but were not significantly different between the smartphone and embedded systems. Practitioner Summary: The findings show that embedded system and portable device voice interfaces place fewer visual demands on the driver than manual interfaces, but they also underscore how differences in system designs can significantly affect not only the demands placed on drivers, but also the successful completion of tasks.

Test track evaluation of headlight glare associated with adaptive curve HID, fixed HID, and fixed halogen low beam headlights.

Adaptive curve headlights swivel with steering input and are linked to reduced insurance claims and improved visual performance. This study assessed glare experienced from adaptive curve high-intensity discharge (HID), fixed (non-swiveling) HID and fixed halogen headlights - all tested in low beam mode. Twenty participants rated glare from vehicles' headlights using the DeBoer visual discomfort scale as a test driver drove towards them from five approaches on a test track. Participants rated the fixed halogen condition as less glaring than the adaptive curve and fixed HID conditions. There was no significant difference in ratings between the HID low-beam conditions. Collapsing across roadway approaches, the mean subjective ratings for the fixed halogen, adaptive curve HID and fixed HID low-beam conditions indicated 'satisfactory' levels of glare. Differences between subjective ratings were supported by illuminance data. Differences among the three low-beam systems appear minor, relative to their differences from a benchmark high-beam condition. Practitioner Summary: Insurance data indicates reduced claims associated with adaptive curve lighting. The current effort was to study how such lighting affects discomfort glare of oncoming drivers relative to conventional headlights. Participants rated halogen headlights as less glaring than fixed and adaptive curve HID low beams. Differences among systems were small and associated with acceptable levels of discomfort glare.

Observed activation status of lane departure warning and forward collision warning of Honda vehicles at dealership service centers.

OBJECTIVE: There are little objective data on whether drivers with lane departure warning and forward collision warning systems actually use them, but self-report data indicate that lane departure warning may be used less and viewed less favorably than forward collision warning. The current study assessed whether the systems were turned on when drivers brought their vehicles to dealership service stations and whether the observational protocol is a feasible method for collecting similar data on various manufacturers' systems. METHODS: Observations of 2013-2015 Honda Accords, 2014-2015 Odysseys, and 2015 CR-Vs occurred at 2 U.S. Honda dealerships for approximately 4 weeks during Summer 2015. RESULTS: Of the 265 vehicles observed to have the 2 systems, 87 (32.8%) had lane departure warning turned on. Accords were associated with a 66% increase in the likelihood that lane departure warning was turned on compared with Odysseys, but the rate was still only about 40% in Accords. In contrast, forward collision warning was turned on in all but one of the observed vehicles. CONCLUSIONS: Observations found that the activation rate was much higher for forward collision warning than lane departure warning. The observation method worked well and appears feasible for extending to other manufacturers.

Multi-modal assessment of on-road demand of voice and manual phone calling and voice navigation entry across two embedded vehicle systems.

One purpose of integrating voice interfaces into embedded vehicle systems is to reduce drivers' visual and manual distractions with 'infotainment' technologies. However, there is scant research on actual benefits in production vehicles or how different interface designs affect attentional demands. Driving performance, visual engagement, and indices of workload (heart rate, skin conductance, subjective ratings) were assessed in 80 drivers randomly assigned to drive a 2013 Chevrolet Equinox or Volvo XC60. The Chevrolet MyLink system allowed completing tasks with one voice command, while the Volvo Sensus required multiple commands to navigate the menu structure. When calling a phone contact, both voice systems reduced visual demand relative to the visual-manual interfaces, with reductions for drivers in the Equinox being greater. The Equinox 'one-shot' voice command showed advantages during contact calling but had significantly higher error rates than Sensus during destination address entry. For both secondary tasks, neither voice interface entirely eliminated visual demand. Practitioner Summary: The findings reinforce the observation that most, if not all, automotive auditory-vocal interfaces are multi-modal interfaces in which the full range of potential demands (auditory, vocal, visual, manipulative, cognitive, tactile, etc.) need to be considered in developing optimal implementations and evaluating drivers' interaction with the systems. Social Media: In-vehicle voice-interfaces can reduce visual demand but do not eliminate it and all types of demand need to be taken into account in a comprehensive evaluation.

On-road experiment to assess drivers' detection of roadside targets as a function of headlight system, target placement, and target reflectance.

Adaptive headlights swivel with steering input to keep the beams on the roadway as drivers negotiate curves. To assess the effects of this feature on driver's visual performance, a field experiment was conducted at night on a rural, unlit, and unlined two-lane road during which 20 adult participant drivers searched a set of 60 targets. High- (n=30) and low- (n=30) reflectance targets were evenly distributed on straight road sections and on the inside or outside of curves. Participants completed three target detection trials: once with adaptive high-intensity discharge (HID) headlights, once with fixed HID headlights, and once with fixed halogen headlights. Results indicated the adaptive HID headlights helped drivers detect targets that were most difficult to see (low reflectance) at the points in curves found by other researchers to be most crucial for successful navigation (inside apex). For targets placed on straight stretches of road or on the outside of curves, the adaptive feature provided no significant improvement in target detection. However, the pattern of results indicate that HID lamps whether fixed or adaptive improved target detection somewhat, suggesting that part of the real world crash reduction measured for this adaptive system (Highway Loss Data Institute (HLDI), 2012a) may be due to the differences in the light source (HID vs. halogen). Depending on the scenario, the estimated benefits to driver response time associated with the tested adaptive (swiveling HID) headlights ranged from 200 to 380ms compared with the fixed headlight systems tested.

The effects of external motivation and real-time automated feedback on speeding behavior in a naturalistic setting.

OBJECTIVE: In this field experiment, the authors tested an alerting system and a monetary incentive system with the objective of reducing speeding more than 5 mph faster than the posted speed limit. BACKGROUND: Speeding is a factor in a significant number of traffic fatalities. The systems tested in this project have been evaluated outside but not within the United States. These studies indicated that similar systems led to reductions in speeding. METHOD: For this study, eight vehicles were instrumented such that vehicle speed and speed limits were linked in real time. A total of 50 participants drove assigned vehicles for 4 weeks. Week 1 was a baseline period; during Week 2 or Week 3, 40 participants experienced the alerting system that issued auditory and visual advisory signals when drivers exceeded the limit by 5 mph or more. Of these 40 individuals, 20 experienced the monetary incentive system during Weeks 2 and 3; Week 4 was a return-to-baseline period. A control group of 10 drivers experienced neither system during the study. RESULTS: Results indicated that the incentive system resulted in significant reductions in driving faster than the posted limit, and the feedback system led to modest changes in speeding. In the condition in which drivers experienced the feedback and incentive, reductions in speeding were similar to those found during the incentive-only condition. CONCLUSION: The technology tested in this study has potential to benefit traffic safety by reducing the incidence of driving faster than the posted limit, which should lead to a reduction in speed-related crashes. APPLICATION: Insurers provide incentive-based discounts on premiums. Combining this technology with such a discount program may improve traffic safety significantly.

A simulator evaluation of the effects of attention maintenance training on glance distributions of younger novice drivers inside and outside the vehicle.

Driver distraction inside and outside the vehicle is increasingly a problem, especially for younger drivers. In many cases the distraction is associated with long glances away from the forward roadway. Such glances have been shown to be highly predictive of crashes. Ideally, one would like to develop and evaluate a training program which reduced these long glances. Thus, an experiment was conducted in a driving simulator to test the efficacy of a training program, FOCAL, that was developed to teach novice drivers to limit the duration of glances that are inside the vehicle while performing an in-vehicle task, such as looking for a CD or finding the 4-way flashers. The test in the simulator showed that the FOCAL trained group performed significantly better than the placebo trained group on several measures, notably on the percentage of within-vehicle glances that were greater than 2, 2.5, and 3 s. However, the training did not generalize to glances away from the roadway (e.g., when drivers were asked to attend to a sign adjacent to the roadway, both trained and untrained novice drivers were equally likely to make especially long glances at the sign).

Using naturalistic driving data to identify variables associated with infrequent, occasional, and consistent seat belt use.

Seat belt use is one of the most effective countermeasures to reduce traffic fatalities and injuries. The success of efforts to increase use is measured by road side observations and self-report questionnaires. These methods have shortcomings, with the former requiring a binary point estimate and the latter being subjective. The 100-car naturalistic driving study presented a unique opportunity to study seat belt use in that seat belt status was known for every trip each driver made during a 12-month period. Drivers were grouped into infrequent, occasional, or consistent seat belt users based on the frequency of belt use. Analyses were then completed to assess if these groups differed on several measures including personality, demographics, self-reported driving style variables as well as measures from the 100-car study instrumentation suite (average trip speed, trips per day). In addition, detailed analyses of the occasional belt user group were completed to identify factors that were predictive of occasional belt users wearing their belts. The analyses indicated that consistent seat belt users took fewer trips per day, and that increased average trip speed was associated with increased belt use among occasional belt users. The results of this project may help focus messaging efforts to convert occasional and inconsistent seat belt users to consistent users.

Using accelerator pedal force to increase seat belt use of service vehicle drivers.

This study evaluated a device that applied a sustained increase in accelerator pedal back force whenever drivers exceeded a preset speed criterion without buckling their seat belts. This force was removed once the belt was fastened. Participants were 6 commercial drivers who operated carpet-cleaning vans. During baseline, no contingency was in place for unbuckled trips. The pedal resistance was introduced via a multiple baseline design across groups. On the first day of treatment, the device was explained and demonstrated for all drivers of the vehicle. The treatment was associated with an immediate sustained increase in seat belt compliance to 100%. Occasionally, drivers initially did not buckle during a trip and encountered the force. In all instances, they buckled within less than 25 s. These results suggest that the increased force was sufficient to set up an establishing operation to reinforce seat belt buckling negatively. Drivers indicated that they were impressed with the device and would not drive very long unbelted with the pedal force in place.

Increasing seat belt use in service vehicle drivers with a gearshift delay.

This study evaluated a device that prevents drivers from shifting vehicles into gear for up to 8 s unless seat belts are buckled. Participants were 101 commercial drivers who operated vans, pickups, or other light trucks from the U.S. and Canada. The driver could escape or avoid the delay by fastening his or her seat belt before shifting out of park. Unbelted participants experienced either a constant delay (8 s) or a variable delay (M  =  8 s). A 16-s delay was introduced for those U.S. drivers who did not show significant improvement. Seat belt use increased from 48% to 67% (a 40% increase) for U.S. drivers and from 54% to 74% (a 37% increase) for Canadian drivers. The fixed delay was more effective for U.S. drivers than the variable delay, but there was no difference between these two delay schedules for Canadian drivers. After the driver fastened his or her seat belt, it tended to remain fastened for the duration of the trip.

Individual differences in route-learning strategy and associated working memory resources.

OBJECTIVE: The current investigation examined individual differences in route-learning strategies and their relative demands on visuospatial versus verbal working memory (WM) resources in virtual environments. BACKGROUND: Learning new routes is a resource-demanding activity that must often be carried out in conjunction with other concurrent tasks. Virtual environments (VEs) are increasingly being used for training and research, pointing to the importance of determining the strategies people use to learn routes in these environments. METHODS: Participants classified as having good or poor sense of direction (SOD) attempted to learn novel routes while concurrently performing either a verbal (articulatory suppression) or a visuospatial (tapping) WM interference task. RESULTS: Different navigational strategies were observed in each SOD group. Individuals with poor SOD relied more heavily on verbal rather than visuospatial WM resources, as evidenced by greater disruption to route-learning performance from the articulatory suppression task relative to the tapping task. Conversely, individuals with good SOD exhibited more route-learning disruption from the tapping task, suggesting a greater reliance on visuospatial WM resources. CONCLUSION: Individuals differ from one another in the strategies they use and the WM resources they tap--verbal or visuospatial--to learn routes in VEs. Self-report measures can be used as indices of such individual differences in navigational strategy use in VE tasks. APPLICATION: Assessing SOD and associated WM resources have implications for targeted training for navigation in VEs and for the design of in-vehicle navigation systems.