Computer Simulation to Assess Emergency Department Length of Stay in Pediatric Traumatic Brain Injury

OBJECTIVES

Our study aimed to identify how emergency department (ED) arrival rate, process of care, and physical layout can impact ED length of stay (LOS) in pediatric traumatic brain injury care.

METHODS

Process flows and value stream maps were developed for 3 level I pediatric trauma centers. Computer simulation models were also used to examine "what if" scenarios based on ED arrival rates.

RESULTS

Differences were observed in prearrival preparation time, ED physical layouts, and time spent on processes. Shorter prearrival preparation time, trauma bed location far from diagnostic or treatment areas, and ED arrival rates that exceed 20 patients/day prolonged ED LOS. This was particularly apparent in 1 center where computer simulation showed that relocation of trauma beds can reduce ED LOS regardless of the number of patients that arrive per day.

CONCLUSIONS

Exceeding certain threshold ED arrival rates of children with traumatic brain injury can substantially increase pediatric trauma center ED LOS but modifications to ED processes and bed location may mitigate this increase.

Driving characteristics of young adults prior to and following concussion

OBJECTIVES

This study sought to examine whether young adults who sustain concussions have different driving histories and pre-injury driving styles than uninjured peers. In addition, we assessed whether modifications were made to driving behavior in the acute period following concussion.

METHODS

Self-reported driving and demographic information was collected from 102 16- to 25-year-old drivers. Half of the sample had recently sustained concussions and the other half comprised a matched comparison group.

RESULTS

The groups reported similar pre-injury driving behaviors and styles. However, the recently injured group had more driving citations, higher rates of psychiatric disorders, and greater likelihood of having sustained a prior concussion. Self-reported driving habits postconcussion suggested that most drivers did not modify their driving behavior following concussion, though they were less likely to drive at night or with others in the car.

CONCLUSION

Results highlight the need for postconcussion driving guidelines and support for returning to driving safely.

Cognitive Impairment and Driving Skills in Youth After Concussion

Abstract Concussions can impact cognitive processes necessary for driving. Young adults, a group who are more likely to engage in risky behaviors, have limited driving experience and a higher rate of motor vehicle collisions; they may be at higher risk for driving impairment after concussion. There are no clear guidelines for return-to-driving following a concussion. We sought to examine the simulated driving performance of young drivers after receiving medical care following a concussion, compared with a similar control population, to examine the association of driving performance with performance on neuropsychological tests. We evaluated 47 drivers, 16- to 25-year-old, within 3 weeks of sustaining a concussion and 50 drivers with similar characteristics who had not sustained concussions. Participants completed demographic questionnaires, the Sport Concussion Assessment Tool-5 (SCAT-5), and a brief set of neurocognitive tests, including the National Institutes of Health (NIH) Toolbox Cognition Battery and the Trail Making Test, and a simulated driving assessment. At various times during simulated driving, participants were asked to respond to tactile stimuli using the tactile detection response task (TDRT), a validated method of testing cognitive load during simulated driving. The concussion group reported significantly higher symptoms on the SCAT-5 than the comparison group. Performance on crystallized neurocognitive skills was similar between groups. Performance on fluid neurocognitive skills was significantly lower in the concussion than comparison group, although scores were in the normal range for both groups. Simulated driving was similar between groups, although there was a small but significant difference in variation in speed as well as TDRT miss rate, with worse performance by the concussion group. Symptom report on the SCAT-5 was significantly associated with TDRT miss rate. In addition, neurocognitive test scores significantly predicted TDRT reaction time and miss count with medium to large effect sizes. Results suggest that neurocognitive screening may be a useful tool for predicting capacity to return to drive. However, further research is needed to determine guidelines for how neuropsychological tests can be used to make return to driving recommendations and to evaluate effects of concussion on real world driving.

Provider perceptions of severe pediatric traumatic brain injury care priorities across hospitals in South America before and during the COVID-19 pandemic

Background

To understand provider perceptions of the COVID-19 pandemic on priorities of severe pediatric traumatic brain injury (TBI) care across hospitals in South America.

Methods

Site principal investigators (PIs) from 17 hospitals in South America enrolled in the PEGASUS-Argentina randomized controlled trial completed questionnaires regarding order of tasks performed in the care of a typical pediatric patient with severe TBI before (2019) and during (2021) the COVID-19 pandemic. Acute care processes were examined by quintiles to identify early, mid, and late actions and were categorized and compared. Associations of hospital volume and subspecialty resource availability with prioritization of key process actions were examined.

Finding

Site PIs from 15 and 16 hospitals completed the surveys in 2019 and 2021, respectively, including 14 who completed both. Action category order was stable between 2019 and 2021 and were ranked in priorities as: initial encounter, primary survey, interventions and invasive monitors, diagnostics, medications, staff communication, then disposition (in 2019) or nutrition (in 2021). There was variation in specific action order between hospitals at both timepoints, with only a few initial encounter and disposition actions limited to a single quintile. There was no reported association between hospital volume or subspecialty resource availability with prioritization of key process actions.

Interpretation

Despite novel healthcare challenges presented by the COVID-19 pandemic, providers in South America perceived maintaining standard severe pediatric TBI care consistent with BTF guidelines. There was large variability in specific action order between individual hospitals reported.

Driving behavior at midblock crosswalks with Rectangular Rapid Flashing Beacons: Hidden Markov model approach using naturalistic data

Pedestrian fatalities have increased in the U.S. with the largest increase being observed on urban arterials and away from intersections. Rectangular Rapid Flashing Beacon (RRFB) has been widely implemented as a safety countermeasure to improve driver awareness and visibility of pedestrians, especially for midblock crosswalks. Studies show that drivers are more likely to yield to pedestrians at crosswalks with an RRFB. These studies are often based on a binary outcome of whether or not drivers yield to pedestrians. Nevertheless, it is also important to consider the drivers' deceleration behavior as a dynamic process at these crosswalks and the impact of pedestrians being present or not. Understanding this dynamic behavior and the related circumstances can provide information on the design of alerting systems that help drivers make more appropriate decisions at these crosswalks to avoid a vehicle-pedestrian crash. This study examined this research topic using Hidden Markov Models (HMMs) and data from a naturalistic study. More specifically, four HMMs were applied to the naturalistic brake and jerk data from the Safety Pilot Model Deployment (SPMD) program given drivers' intention to slow down, the RRFB activation status, and the presence of pedestrians. The time-based data sequence was converted to distance-based through a moving window to enhance result comparison and interpretation. Grid-search was used to select the best moving window parameters and the optimal number of hidden states. This study confirmed the high compliance at an activated RRFB when pedestrians were present. Even without pedestrians, one in five traversals showed drivers slowing down to less than 8.94 m/s (20 mph) within 35 m of the crosswalk. Model results further indicate that drivers started braking as far back as 180 m before the crosswalk and stopped braking from 70 m before the crosswalk at an activated RRFB without pedestrians. When there were pedestrians, drivers would start braking 20 to 30 m later but would brake more firmly and for longer. Finally, drivers were not likely to brake or decelerate when RRFB was off and no pedestrians were present.

Sparse group regularization for semi-continuous transportation data

Motor vehicle crashes are a global public health concern. Most analysis have used zero-inflated count models for examining crash counts. However, few methods are available to account for safety metrics that have semi-continuous observations. This article considers the problem of variable selection for the semi-continuous zero-inflated (SCZI) models. These models include two parts: a zero-inflated part and a nonzero continuous part. A special group regularization is designed to accommodate the unique structure of two-part SCZI models, and a type of Bayesian information criterion is proposed to select tuning parameters. We illustrate the variable selection process of the proposed model using lane position data from a driving simulator study. In the study, drivers stay in the intended lane for the majority of their drive (zero-inflated part). On occasion, some drivers do drift out of their intended driving lane (nonzero continuous part). Our findings show that individual differences can be captured with the proposed model, which has implications for driving safety and the design of in-vehicle alerting systems.

Auditory Messages for Intersection Movement Assist (IMA) Systems: Effects of Speech- and Nonspeech-Based Cues

OBJECTIVE

The objective of this study was to assess the effects of different warning messages for an Intersection Movement Assist (IMA) based on drivers' ability to avoid a potential safety hazard.

BACKGROUND

An IMA system can detect hazards and warn drivers when it is unsafe to enter an intersection. The effects of different warning information conveyed by these systems are still unknown.

METHOD

A driving simulator study with 80 participants was conducted with a red light running (RLR) scenario using a 5 (warnings) x 2 (training) between-subject design. IMA warnings included the messages "Danger," "Brake now," "Vehicle on your left," a beep, and no IMA warning. Training was provided to half of the participants. Analysis of variance and logistic regression models were used to examine differences in drivers' avoidance behavior.

RESULTS

The analyses showed that all tested warning messages can significantly enhance drivers' avoidance performance. Significant differences were observed in crash occurrence, avoidance behavior (i.e., reaction time and speed change), and eye movements (i.e., fixation pattern and time to first fixation). The effects of training also differed given the warning message provided.

CONCLUSION

The "Brake now" message performed best in reducing crash involvement and prompted better avoidance performance. The "Danger" and "Vehicle on your left" messages improved drivers' hazard detection ability. The training showed a potential to enhance the effectiveness of nonspeech warning messages.

APPLICATION

The findings of this study can help designers and engineers better design IMA warning messages for RLR scenarios.

Allocation of Driver Attention for Varying In-Vehicle System Modalities

OBJECTIVE

This paper examines drivers' allocation of attention using response time to a tactile detection response task (TDRT) while interacting with an in-vehicle information system (IVIS) over time.

BACKGROUND

Longer TDRT response time is associated with higher cognitive workload. However, it is not clear what role is assumed by the human and system in response to varying in-vehicle environments over time.

METHOD

A driving simulator study with 24 participants was conducted with a restaurant selection task of two difficulty levels (easy and hard) presented in three modalities (audio only, visual only, hybrid). A linear mixed-effects model was applied to identify factors that affect TDRT response time. A nonparametric time-series model was also used to explore the visual attention allocation under the hybrid mode over time.

RESULTS

The visual-only mode significantly increased participants' response time compared with the audio-only mode. Females took longer to respond to the TDRT when engaged with an IVIS. The study showed that participants tend to use the visual component more toward the end of the easy tasks, whereas the visual mode was used more at the beginning of the harder tasks.

CONCLUSION

The visual-only mode of the IVIS increased drivers' cognitive workload when compared with the auditory-only mode. Drivers showed different visual attention allocation during the easy and hard restaurant selection tasks in the hybrid mode.

APPLICATION

The findings can help guide the design of automotive user interfaces and help manage cognitive workload.

Comparisons of physical exposure between workers harvesting apples on mobile orchard platforms and ladders, part 1: Back and upper arm postures

This study compared farmworkers' exposure to non-neutral postures using a new mobile platform apple harvesting method and the traditional method using ladders. Twenty-four workers were recruited and assigned into three groups: ladder workers (n = 8) picking apples from full trees using a ladder, mobile platform workers (n = 8) picking apples from upper part of the trees while standing on a moving platform, and ground-based mobile platform workers (n = 8) picking apples from lower part of the trees which the mobile platform workers left out. Upper arm and back inclinations were continuously monitored during harvesting using tri-axial accelerometers over full work shifts (~8 h). Upper arm posture was characterized as the percentage of time that upper arm flexion and abduction exceeded 30°, 60°, and 90°. Back posture was characterized as the percentage of time that torso angles (sagittal flexion or lateral bending) exceeded 10°, 20°, and 30°. The 10th, 50th, and 90th postural percentiles were also calculated. The platform workers had lower exposures to upper arm flexion and abduction than the ground and ladder workers. There were no differences in torso angles between the ladder and mobile platform workers; however, the ground workers were exposed to more and greater percentages of time in torso flexions.

Comparisons of physical exposure between workers harvesting apples on mobile orchard platforms and ladders, part 2: Repetitive upper arm motions

Farmworkers are exposed to physical risk factors including repetitive motions. Existing ergonomic assessment methods are primarily laboratory-based and, thus, inappropriate for use in the field. This study presents an approach to characterize the repetitive motions of the upper arms based on direct measurement using accelerometers. Repetition rates were derived from upper arm inclination data and with video recordings in the field. This method was used to investigate whether harvesting with mobile platforms (teams harvesting apples from the platform and the ground) increased the farmworkers' exposure to upper arm repetitive motions compared to traditional harvesting using ladders. The ladder workers had higher repetitive motions (13.7 cycles per minute) compared to the platform and ground workers (11.7 and 12.2 cycles per minutes). The higher repetitions in the ladder workers were likely due to their ability to work independently and the additional arm movements associated with ladder climbing and walking.

Human factors considerations in designing a personalized mobile dialysis device: An interview study

Recent technical advances have enabled the creation of mobile dialysis device prototypes. These prototypes have been tested for their ability to allow an individual to be dialyzed continuously rather than sporadically. The most recent prototype of a mobile dialysis device aims at increased functionality, which suggests that human factors issues (e.g., efficiency, bulkiness, and weight) are now considered carefully. This study describes advances in the design of an Ambulatory Kidney to Improve Vitality (AKTIV), using an interview protocol during the early stages of product development to capture patients' and caregivers' reactions. The AKTIV has the potential to improve patients' quality of life and decrease mortality rates. The goal of our study is to examine patients' and caregivers' design preferences and feature considerations for an AKTIV. We interviewed 22 participants (age M = 57.50, SD = 13.30), of whom 12 were female and 16 were patients. A pre-interview survey was distributed to the participants, and semi-structured interviews were subsequently held. The pre-interview results show that the belt and backpack designs were preferred over the shoulder bag and distributed designs. The participants also indicated on their pre-interview forms that safety and accuracy were more important to them than attachment ease, comfort, compactness, or operational simplicity. Invisibility and mobility were frequently mentioned when determining the strengths of each of the five design types during the interviews. Finally, individual differences in preferences for the various design types and attributes were identified. The results from our study have important implications for improving efficiency, effectiveness, and user satisfaction in relation to AKTIV prototypes and products. The findings from this interview study will help to ensure engineers and clinicians have target parameters for redesigning the AKTIV.

Intersections and Non-Intersections: A Protocol for Identifying Pedestrian Crash Risk Locations in GIS

Intersection and non-intersection locations are commonly used as spatial units of analysis for modeling pedestrian crashes. While both location types have been previously studied, comparing results is difficult given the different data and methods used to identify crash-risk locations. In this study, a systematic and replicable protocol was developed in GIS (Geographic Information System) to create a consistent spatial unit of analysis for use in pedestrian crash modelling. Four publicly accessible datasets were used to identify unique intersection and non-intersection locations: Roadway intersection points, roadway lanes, legal speed limits, and pedestrian crash records. Two algorithms were developed and tested using five search radii (ranging from 20 to 100 m) to assess the protocol reliability. The algorithms, which were designed to identify crash-risk locations at intersection and non-intersection areas detected 87.2% of the pedestrian crash locations (r: 20 m). Agreement rates between algorithm results and the crash data were 94.1% for intersection and 98.0% for non-intersection locations, respectively. The buffer size of 20 m generally showed the highest performance in the analyses. The present protocol offered an efficient and reliable method to create spatial analysis units for pedestrian crash modeling. It provided researchers a cost-effective method to identify unique intersection and non-intersection locations. Additional search radii should be tested in future studies to refine the capture of crash-risk locations.

Identifying characteristics that impact motor carrier safety using Bayesian networks

PROBLEM STATEMENT

In the U.S., a safety rating is assigned to each motor carrier based on data obtained from the Motor Carrier Management Information System (MCMIS) and an on-site investigation. While researchers have identified variables associated with the safety ratings, the specific direction of the relationships are not necessarily clear.

OBJECTIVE

The objective of this study is to identify those relationships involved in the safety ratings of interstate motor carriers, the largest users of the U.S. transportation network.

METHOD

Bayesian networks are used to learn these relationships from data obtained from MCMIS for a 6-year period (2007-2012).

RESULTS

Our study shows that safety rating assignment is a complex process with only a subset of the variables having statistically significant relationship with safety rating. They include driver out-of-service violations, weight violations, traffic violations, fleet size, total employed drivers, and passenger & general carrier indicators.

APPLICATION

The findings have both immediate implications and long term benefits. The immediate implications relate to better identification of unsafe motor carriers, and the long term benefits pertain to policies and crash countermeasures that can enhance carrier safety.

Behavioral Adaptations to Lane Keeping Systems: Effects of Exposure and Withdrawal

OBJECTIVE

A driving simulator study was conducted to evaluate the longitudinal effects of an intervention and withdrawal of a lane keeping system on driving performance and cognitive workload.

BACKGROUND

Autonomous vehicle systems are being implemented into the vehicle fleet. However, limited research exists in understanding the carryover effects of long-term exposure.

METHODS

Forty-eight participants (30 treatment, 18 control) completed eight drives across three separate days in a driving simulator. The treatment group had an intervention and withdrawal of a lane keeping system. Changes in driving performance (standard deviation of lateral position [SDLP] and mean time to collision [TTC]) and cognitive workload (response time and miss rate to a detection response task) were modeled using mixed effects linear and negative binomial regression.

RESULTS

Drivers exposed to the lane keeping system had an increase in SDLP after the system was withdrawn relative to their baseline. Drivers with lane keeping had decreased mean TTC during and after system withdrawal compared with manual drivers. There was an increase in cognitive workload when the lane keeping system was withdrawn relative to when the system was engaged.

CONCLUSION

Behavioral adaptations in driving performance and cognitive workload were present during automation and persisted after the automation was withdrawn.

APPLICATION

The findings of this research emphasize the importance to consider the effects of skill atrophy and misplaced trust due to semi-autonomous vehicle systems. Designers and policymakers can utilize this for system alerts and training.

Evaluating variability in foot to pedal movements using functional principal components analysis

There are reasons why the driver's foot may not be applied to the correct pedal while driving and this can lead to unintended consequences. In this study, we seek to capture common and unique patterns of variations in drivers' foot movements using functional principal components analysis (FPCA). This analysis technique was used to analyze three categories of pedal response types (direct hits, corrected trajectories, and pedal errors) based on the various foot to pedal trajectories. Data from a driving simulator study with video data of foot movements for 45 drivers was used for analyses. Most foot movements show common patterns associated with direct hits and corrected trajectories with some level of variation. However, those foot movements associated with unique patterns might be early indicators of pedal errors. The findings of this study can be used with collision mitigation systems to provide early detection of foot trajectories that are more likely to result in a pedal error.

Drivers’ Avoidance Strategies When Using a Forward Collision Warning (FCW) System

Forward collision warning (FCW) systems help prevent rear-end collisions by identifying and alerting drivers of threats ahead. Understanding drivers’ avoidance strategies i.e. the tendency to brake or steer is important for the design and effectiveness of these systems. A driving simulator study was performed across five US locations to examine three driver avoidance maneuvers: braking only, steering only and combined braking and steering. A log-linear analysis was used to investigate the likelihood of an avoidance maneuver given the driver characteristics (age, gender) and study location. Findings showed that drivers aged 40 years and older were more likely to use a combined braking and steering maneuver to avoid a rearend collision. Drivers from two coastal urban areas (Washington, D.C. and Seattle, WA) were less likely to choose braking only in response to FCW alerts. Younger drivers and drivers that live in more rural areas (Clemson, SC and Iowa City, IA) were more likely to select braking only to avoid a crash, which could be due to their experience in less congested traffic environment. The findings of this study provide some insights on the factors associated with various avoidance strategies among drivers. This understanding can help guide the design of future in-vehicle collision warning systems.

Driver adaptation to lane keeping assistance systems: Do drivers become less vigilant?

Driver adaptation to semi-autonomous vehicles is examined in this study using a longitudinal driving simulator study with 18 subjects randomly assigned to a control (n = 9) and treatment (n = 9) group. A Tactile Detection Response Task (TDRT) was used to measure cognitive workload while drivers engaged in visual-manual distracting tasks using an in-vehicle information system, with and without a lane-keeping assistance system (baseline, intervention, and withdrawal period). Measures of miss rate and reaction time to the TDRT stimuli suggest that drivers in both groups showed decreases in cognitive workload as they gained experience. Participants in the treatment group experienced higher cognitive workload when the lane keeping assistance system was withdrawn. On average, there were greater decreases in cognitive workload over time for the difficult tasks as compared to the easy tasks for both the control and treatment groups. The effect was more pronounced in the control group with larger decreases in cognitive workload. The NASA TLX was also comparable to the task accuracy. These results suggest that adaptations in driver behavior due to exposure to automation may have transfer effects on cognitive workload and thus may lead to safety implications.

Frequency of and factors associated with emergency department intracranial pressure monitor placement in severe paediatric traumatic brain injury

OBJECTIVE

To examine the frequency of and factors associated with emergency department (ED) intracranial pressure (ICP) monitor placement in severe paediatric traumatic brain injury (TBI).

METHODS

Retrospective, multicentre cohort study of children <18 years admitted to the ED with severe TBI and intubated for >48 hours from 2007 to 2011.

RESULTS

Two hundred and twenty-four children had severe TBI and 75% underwent either ED, operating room (OR) or paediatric intensive care unit (PICU) ICP monitor placement. Four out of five centres placed ICP monitors in the ED, mostly (83%) fibreoptic. Nearly 40% of the patients who received ICP monitors get it placed in the ED (29% overall). Factors associated with ED ICP monitor placement were as follows: age 13 to <18 year olds compared to infants (aRR 2.02; 95% CI 1.37, 2.98), longer ED length of stay (LOS) (aRR 1.15; 95% CI 1.08, 1.21), trauma centre designation paediatric only I/II compared to adult/paediatric I/II (aRR 1.71; 95% CI 1.48, 1.98) and higher mean paediatric TBI patient volume (aRR 1.88;95% CI 1.68, 2.11). Adjusted for centre, higher bedside ED staff was associated with longer ED LOS (aRR 2.10; 95% CI 1.06, 4.14).

CONCLUSION

ICP monitors are frequently placed in the ED at paediatric trauma centres caring for children with severe TBI. Both patient and organizational level factors are associated with ED ICP monitor placement.

Foot placement during error and pedal applications in naturalistic driving

Data from a naturalistic driving study was used to examine foot placement during routine foot pedal movements and possible pedal misapplications. The study included four weeks of observations from 30 drivers, where pedal responses were recorded and categorized. The foot movements associated with pedal misapplications and errors were the focus of the analyses. A random forest algorithm was used to predict the pedal application types based the video observations, foot placements, drivers' characteristics, drivers' cognitive function levels and anthropometric measurements. A repeated multinomial logit model was then used to estimate the likelihood of the foot placement given various driver characteristics and driving scenarios. The findings showed that prior foot location, the drivers' seat position, and the drive sequence were all associated with incorrect foot placement during an event. The study showed that there is a potential to develop a driver assistance system that can reduce the likelihood of a pedal error.

Decisions and actions of distracted drivers at the onset of yellow lights

Driving on an approach to a signalized intersection while distracted is relatively risky, as potential vehicular conflicts and resulting angle collisions tend to be relatively more severe compared to other locations. Given the prevalence and importance of this particular scenario, the objective of this study was to examine the decisions and actions of distracted drivers during the onset of yellow lights. Driving simulator data were obtained from a sample of 69 drivers under baseline and handheld cell phone conditions at the University of Iowa - National Advanced Driving Simulator. Explanatory variables included age, gender, cell phone use, distance to stop-line, and speed. Although there is extensive research on drivers' responses to yellow traffic signals, the examinations have been conducted from a traditional regression-based approach, which do not necessary provide the underlying relations and patterns among the sampled data. In this paper, we exploit the benefits of both classical statistical inference and data mining techniques to identify the a priori relationships among main effects, non-linearities, and interaction effects. Results suggest that the probability of yellow light running increases with the increase in driving speed at the onset of yellow. Both young (18-25 years) and middle-aged (30-45 years) drivers reveal reduced propensity for yellow light running whilst distracted across the entire speed range, exhibiting possible risk compensation during this critical driving situation. The propensity for yellow light running for both distracted male and female older (50-60 years) drivers is significantly higher. Driver experience captured by age interacts with distraction, resulting in their combined effect having slower physiological response and being distracted particularly risky.

Variation in seizure prophylaxis in severe pediatric traumatic brain injury

OBJECTIVE Posttraumatic seizure is a major complication following traumatic brain injury (TBI). The aim of this study was to determine the variation in seizure prophylaxis in select pediatric trauma centers. The authors hypothesized that there would be wide variation in seizure prophylaxis selection and use, within and between pediatric trauma centers. METHODS In this retrospective multicenter cohort study including 5 regional pediatric trauma centers affiliated with academic medical centers, the authors examined data from 236 children (age < 18 years) with severe TBI (admission Glasgow Coma Scale score ≤ 8, ICD-9 diagnosis codes of 800.0-801.9, 803.0-804.9, 850.0-854.1, 959.01, 950.1-950.3, 995.55, maximum head Abbreviated Injury Scale score ≥ 3) who received tracheal intubation for ≥ 48 hours in the ICU between 2007 and 2011. RESULTS Of 236 patients, 187 (79%) received seizure prophylaxis. In 2 of the 5 centers, 100% of the patients received seizure prophylaxis medication. Use of seizure prophylaxis was associated with younger patient age (p < 0.001), inflicted TBI (p < 0.001), subdural hematoma (p = 0.02), cerebral infarction (p < 0.001), and use of electroencephalography (p = 0.023), but not higher Injury Severity Score. In 63% cases in which seizure prophylaxis was used, the patients were given the first medication within 24 hours of injury, and 50% of the patients received the first dose in the prehospital or emergency department setting. Initial seizure prophylaxis was most commonly with fosphenytoin (47%), followed by phenytoin (40%). CONCLUSIONS While fosphenytoin was the most commonly used medication for seizure prophylaxis, there was large variation within and between trauma centers with respect to timing and choice of seizure prophylaxis in severe pediatric TBI. The heterogeneity in seizure prophylaxis use may explain the previously observed lack of relationship between seizure prophylaxis and outcomes.

A Qualitative Study Exploring Factors Associated with Provider Adherence to Severe Pediatric Traumatic Brain Injury Guidelines

Despite demonstrated improvement in patient outcomes with use of the Pediatric Traumatic Brain Injury (TBI) Guidelines (Guidelines), there are differential rates of adherence. Provider perspectives on barriers and facilitators to adherence have not been elucidated. This study aimed to identify and explore in depth the provider perspective on factors associated with adherence to the Guidelines using 19 focus groups with nurses and physicians who provided acute management for pediatric patients with TBI at five university-affiliated Level 1 trauma centers. Data were examined using deductive and inductive content analysis. Results indicated that three inter-related domains were associated with clinical adherence: 1) perceived guideline credibility and applicability to individual patients, 2) implementation, dissemination, and enforcement strategies, and 3) provider culture, communication styles, and attitudes towards protocols. Specifically, Guideline usefulness was determined by the perceived relevance to the individual patient given age, injury etiology, and severity and the strength of the evidence. Institutional methods to formally endorse, codify, and implement the Guidelines into the local culture were important. Providers wanted local protocols developed using interdisciplinary consensus. Finally, a culture of collaboration, including consistent, respectful communication and interdisciplinary cooperation, facilitated adherence. Provider training and experience, as well as attitudes towards other standardized care protocols, mirror the use and attitudes towards the Guidelines. Adherence was determined by the interaction of each of these guideline, institutional, and provider factors acting in concert. Incorporating provider perspectives on barriers and facilitators to adherence into hospital and team protocols is an important step toward improving adherence and ultimately patient outcomes.

The Effects of Driver Distraction for Individuals With Traumatic Brain Injuries

OBJECTIVE

The aim of this study was to evaluate the effects of secondary tasks on the driving performance of individuals with mild traumatic brain injuries (TBIs).

BACKGROUND

Studies suggest detrimental impacts of driving with TBI or while distracted but the impact of driver distraction on TBI drivers is not well documented.

METHOD

Bayesian regression models were used to estimate the effect of relatively simple secondary tasks on driving performance of TBI and healthy control (HC) drivers. A driving simulator was used to develop prior distribution of task effects on driving performance for HCs. An on-road study was conducted with TBI and HC drivers to generate effect estimates for the posterior distributions. The Bayesian models were also compared to frequentist models.

RESULTS

During a coin-sorting task, all drivers exhibited larger maximum lateral acceleration and larger standard deviation of speed than in a baseline driving segment. There were no significant driving performance differences between the TBI and the HC drivers during the tasks. Across all tasks, TBI drivers spent more time looking at the tasks and made more frequent glances toward the tasks.

CONCLUSIONS

The findings show that even drivers with mild TBI have significantly longer and more glances toward the tasks compared to the HCs.

APPLICATION

This study demonstrates a Bayesian approach and how the results differ from frequentist statistics. Using prior distributions in a Bayesian model helps account for the probabilities associated with otherwise unknown parameters. This method strengthens the Bayesian parameter estimates compared to that of a frequentist model.

Driver's adaptive glance behavior to in-vehicle information systems

The purpose of this study was to examine the adaptive behavior of drivers as they engage with in-vehicle devices over time and in varying driving situations. Behavioral adaptation has been shown to occur among drivers after prolonged use of in-vehicle devices, but few studies have examined drivers' risk levels across different driving demands. A multi-day simulator study was conducted with 28 young drivers (under 30 years old) as they engaged in different text entry and reading tasks while driving in two different traffic conditions. Cluster analysis was used to categorize drivers based on their risk levels and random coefficient models were used to assess changes in drivers' eye glance behavior. Glance duration significantly increased over time while drivers were performing text entry tasks but not for text reading tasks. High-risk drivers had longer maximum eyes-off-road when performing long text entry tasks compared to low-risk drivers, and this difference increased over time. The traffic condition also had a significant impact on drivers' glance behavior. This study suggests that drivers may exhibit negative behavioral adaptation as they become more comfortable with using in-vehicle technologies over time. Results of this paper may provide guidance for the design of in-vehicle devices that adapt based on the context of the situation. It also demonstrates that random coefficient models can be used to obtain better estimations of driver behavior when there are large individual differences.

Is Talking to Your Car Dangerous? It Depends: Prologue to the Special Section

Cognitive distraction represents an important and growing traffic safety issue, particularly with the increasing computerization of cars. The target paper in this special section describes a protocol for assessing the distraction potential of information and entertainment systems. Cognitive distraction has specific relevance to the challenges facing driving safety but also reflects the more pervasive challenge of generalizing findings in the face of complex contextual and compensatory influences. Peer commentaries from five driving safety experts sketch paths forward in assessing the distraction potential of in-vehicle information technology. A simple, definitive statement regarding the risk of talking to your car is appealing, but the complexity of driver behavior may make such a statement unachievable.

Modeling Types of Pedal Applications Using a Driving Simulator

OBJECTIVE

The aim of this study was to examine variations in drivers' foot behavior and identify factors associated with pedal misapplications.

BACKGROUND

Few studies have focused on the foot behavior while in the vehicle and the mishaps that a driver can encounter during a potentially hazardous situation.

METHOD

A driving simulation study was used to understand how drivers move their right foot toward the pedals. The study included data from 43 drivers as they responded to a series of rapid traffic signal phase changes. Pedal application types were classified as (a) direct hit, (b) hesitated, (c) corrected trajectory, and (d) pedal errors (incorrect trajectories, misses, slips, or pressed both pedals). A mixed-effects multinomial logit model was used to predict the likelihood of one of these pedal applications, and linear mixed models with repeated measures were used to examine the response time and pedal duration given the various experimental conditions (stimuli color and location).

RESULTS

Younger drivers had higher probabilities of direct hits when compared to other age groups. Participants tended to have more pedal errors when responding to a red signal or when the signal appeared to be closer. Traffic signal phases and locations were associated with pedal response time and duration. The response time and pedal duration affected the likelihood of being in one of the four pedal application types.

CONCLUSION AND APPLICATION

Findings from this study suggest that age-related and situational factors may play a role in pedal errors, and the stimuli locations could affect the type of pedal application.

The walking environment in Lima, Peru and pedestrian-motor vehicle collisions: an exploratory analysis

OBJECTIVE

Pedestrians comprise 78% of the road fatalities in Peru. The objective of this study was to explore the relationship between the walking environment and pedestrian-motor vehicle collisions.

METHODS

A matched case-control study was used to detect the odds of a pedestrian-motor vehicle collision at a pedestrian crossing location. Data were collected from 11 sampled police commissaries in Lima, Peru.

RESULTS

In a multivariable model adjusting for vehicle and pedestrian flow, pedestrian collisions were less likely in the presence of a curb and sidewalk on both roadway sides (odds ratio [OR] = 0.19, 95% confidence interval [CI], 0.11-0.33) or a pedestrian barricade (OR = 0.11, 95% CI, 0.01-0.81). There was a greater risk of collisions for each street vendor present (OR = 2.82, 95% CI, 1.59-5.00) or whether any parked vehicles (OR = 3.67, 95% CI, 1.18-11.4) were present.

CONCLUSIONS

Improving or addressing these potentially modifiable features of the walking environment could improve pedestrian safety in Lima and in similar urban settings in low- and middle-income countries.

Acute care clinical indicators associated with discharge outcomes in children with severe traumatic brain injury

OBJECTIVE

The effect of the 2003 severe pediatric traumatic brain injury (TBI) guidelines on outcomes has not been examined. We aimed to develop a set of acute care guideline-influenced clinical indicators of adherence and tested the relationship between these indicators during the first 72 hours after hospital admission and discharge outcomes.

DESIGN

Retrospective multicenter cohort study.

SETTING

Five regional pediatric trauma centers affiliated with academic medical centers.

PATIENTS

Children under 18 years with severe traumatic brain injury (admission Glasgow Coma Scale score ≤ 8, International Classification of Diseases, 9th Edition, diagnosis codes of 800.0-801.9, 803.0-804.9, 850.0-854.1, 959.01, 950.1-950.3, 995.55, maximum head abbreviated Injury Severity Score ≥ 3) who received tracheal intubation for at least 48 hours in the ICU between 2007 and 2011 were examined.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Total percent adherence to the clinical indicators across all treatment locations (prehospital, emergency department, operating room, and ICU) during the first 72 hours after admission to study center were determined. Main outcomes were discharge survival and Glasgow Outcome Scale score. Total adherence rate across all locations and all centers ranged from 68% to 78%. Clinical indicators of adherence were associated with survival (adjusted hazard ratios, 0.94; 95% CI, 0.91-0.96). Three indicators were associated with survival: absence of prehospital hypoxia (adjusted hazard ratios, 0.20; 95% CI, 0.08-0.46), early ICU start of nutrition (adjusted hazard ratios, 0.06; 95% CI, 0.01-0.26), and ICU PaCO2 more than 30 mm Hg in the absence of radiographic or clinical signs of cerebral herniation (adjusted hazard ratios, 0.22; 95% CI, 0.06-0.8). Clinical indicators of adherence were associated with favorable Glasgow Outcome Scale among survivors (adjusted hazard ratios, 0.99; 95% CI, 0.98-0.99). Three indicators were associated with favorable discharge Glasgow Outcome Scale: all operating room cerebral perfusion pressure more than 40 mm Hg (adjusted relative risk, 0.61; 95% CI, 0.58-0.64), all ICU cerebral perfusion pressure more than 40 mm Hg (adjusted relative risk, 0.73; 95% CI, 0.63-0.84), and no surgery (any type; adjusted relative risk, 0.68; 95% CI, 0.53- 0.86).

CONCLUSIONS

Acute care clinical indicators of adherence to the Pediatric Guidelines were associated with significantly higher discharge survival and improved discharge Glasgow Outcome Scale. Some indicators were protective, regardless of treatment location, suggesting the need for an interdisciplinary approach to the care of children with severe traumatic brain injury.

Pedestrian signalization and the risk of pedestrian-motor vehicle collisions in Lima, Peru

Safe walking environments are essential for protecting pedestrians and promoting physical activity. In Peru, pedestrians comprise over three-quarters of road fatality victims. Pedestrian signalization plays an important role managing pedestrian and vehicle traffic and may help improve pedestrian safety. We examined the relationship between pedestrian-motor vehicle collisions and the presence of visible traffic signals, pedestrian signals, and signal timing to determine whether these countermeasures improved pedestrian safety. A matched case-control design was used where the units of study were crossing locations. We randomly sampled 97 control-matched collisions (weighted N=1134) at intersections occurring from October, 2010 to January, 2011 in Lima. Each case-control pair was matched on proximity, street classification, and number of lanes. Sites were visited between February, 2011 and September, 2011. Each analysis accounted for sampling weight and matching and was adjusted for vehicle and pedestrian traffic flow, crossing width, and mean vehicle speed. Collisions were more common where a phased pedestrian signal (green or red-light signal) was present compared to no signalization (odds ratio [OR] 8.88, 95% Confidence Interval [CI] 1.32-59.6). A longer pedestrian-specific signal duration was associated with collision risk (OR 5.31, 95% CI 1.02-9.60 per 15-s interval). Collisions occurred more commonly in the presence of any signalization visible to pedestrians or pedestrian-specific signalization, though these associations were not statistically significant. Signalization efforts were not associated with lower risk for pedestrians; rather, they were associated with an increased risk of pedestrian-vehicle collisions.

National variability in intracranial pressure monitoring and craniotomy for children with moderate to severe traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a significant cause of mortality and disability in children. Intracranial pressure monitoring (ICPM) and craniotomy/craniectomy (CRANI) may affect outcomes. Sources of variability in the use of these interventions remain incompletely understood.

OBJECTIVE

To analyze sources of variability in the use of ICPM and CRANI.

METHODS

Retrospective cross-sectional study of patients with moderate/severe pediatric TBI with the use of data submitted to the American College of Surgeons National Trauma Databank.

RESULTS

We analyzed data from 7140 children at 156 US hospitals during 7 continuous years. Of the children, 27.4% had ICPM, whereas 11.7% had a CRANI. Infants had lower rates of ICPM and CRANI than older children. A lower rate of ICPM was observed among children hospitalized at combined pediatric/adult trauma centers than among children treated at adult-only trauma centers (relative risk = 0.80; 95% confidence interval 0.66-0.97). For ICPM and CRANI, 18.5% and 11.6%, respectively, of residual model variance was explained by between-hospital variation in care delivery, but almost no correlation was observed between within-hospital tendency toward performing these procedures.

CONCLUSION

Infants received less ICPM than older children, and children hospitalized at pediatric trauma centers received less ICPM than children at adult-only trauma centers. In addition, significant between-hospital variability existed in the delivery of ICPM and CRANI to children with moderate-severe TBI.

Bus stops and pedestrian-motor vehicle collisions in Lima, Peru: a matched case-control study

OBJECTIVE

To evaluate the relationship between bus stop characteristics and pedestrian-motor vehicle collisions.

METHODS

This was a matched case-control study where the units of study were pedestrian crossings in Lima, Peru. We performed a random sample of 11 police commissaries in Lima, Peru. Data collection occurred from February 2011 to September 2011. A total of 97 intersection cases representing 1134 collisions and 40 mid-block cases representing 469 collisions that occurred between October 2010 and January 2011, and their matched controls, were included. The main exposures assessed were presence of a bus stop and specific bus stop characteristics. The main outcome measure was occurrence of a pedestrian-motor vehicle collision.

RESULTS

Intersections with bus stops were three times more likely to have a pedestrian-vehicle collision (OR 3.28, 95% CI 1.53 to 7.03), relative to intersections without bus stops. Formal and informal bus stops were associated with higher odds of a collision at intersections (OR 6.23, 95% CI 1.76 to 22.0 and OR 2.98, 1.37 to 6.49). At mid-block sites, bus stops on a bus-dedicated transit lane were also associated with collision risk (OR 2.36, 95% CI 1.02 to 5.42). All bus stops were located prior to the intersection, contrary to practices in most high-income countries.

CONCLUSIONS

In urban Lima, the presence of a bus stop was associated with a threefold increase in risk of a pedestrian collision. The highly competitive environment among bus companies may provide an economic incentive for risky practices, such as dropping off passengers in the middle of traffic and jockeying for position with other buses. Bus stop placement should be considered to improve pedestrian safety.

Emerging research methods and their application to road safety

The study of road safety has seen great strides over the past few decades with advances in analytical methods and research tools that allow researchers to provide insights into the complex interactions of the driver, vehicle, and roadway. Data collection methods range from traditional traffic and roadway sensors to instrumented vehicles and driving simulators, capable of providing detailed data on both the normal driving conditions and the circumstances surrounding a safety critical event. In September 2011, the Third International Conference on Road Safety and Simulation was held in Indianapolis, Indiana, USA, which was hosted by the Purdue University Center for Road Safety and sponsored by the Transportation Research Board and its three committees: ANB20 Safety Data, Analysis and Evaluation, AND30 Simulation and Measurement of Vehicle and Operator Performance, and ABJ95 Visualization in Transportation. The conference brought together two hundred researchers from all over the world demonstrating some of the latest research methods to quantify crash causality and associations, and model road safety. This special issue is a collection of 14 papers that were presented at the conference and then peer-reviewed through this journal. These papers showcase the types of analytical tools needed to examine various crash types, the use of naturalistic and on-road data to validate the use of surrogate measures of safety, and the value of driving simulators to examine high-risk situations.

Compulsive cell phone use and history of motor vehicle crash

PURPOSE

Few studies have examined the psychological factors underlying the association between cell phone use and motor vehicle crash. We sought to examine the factor structure and convergent validity of a measure of problematic cell phone use, and to explore whether compulsive cell phone use is associated with a history of motor vehicle crash.

METHODS

We recruited a sample of 383 undergraduate college students to complete an online assessment that included cell phone use and driving history. We explored the dimensionality of the Cell Phone Overuse Scale (CPOS) using factor analytic methods. Ordinary least-squares regression models were used to examine associations between identified subscales and measures of impulsivity, alcohol use, and anxious relationship style, to establish convergent validity. We used negative binomial regression models to investigate associations between the CPOS and motor vehicle crash incidence.

RESULTS

We found the CPOS to be composed of four subscales: anticipation, activity interfering, emotional reaction, and problem recognition. Each displayed significant associations with aspects of impulsivity, problematic alcohol use, and anxious relationship style characteristics. Only the anticipation subscale demonstrated statistically significant associations with reported motor vehicle crash incidence, controlling for clinical and demographic characteristics (relative ratio, 1.13; confidence interval, 1.01-1.26). For each 1-point increase on the 6-point anticipation subscale, risk for previous motor vehicle crash increased by 13%.

CONCLUSIONS

Crash risk is strongly associated with heightened anticipation about incoming phone calls or messages. The mean score on the CPOS is associated with increased risk of motor vehicle crash but does not reach statistical significance.

Driver's lane keeping ability with eyes off road: Insights from a naturalistic study

Many studies have shown that driver inattention can influence lane-keeping ability. The majority of studies on lane keeping have been conducted in controlled on-road networks or in simulated environments. However, few studies have examined lane-keeping ability in naturalistic settings for the same purpose. In this current study, the relationship between driver inattention and lane keeping ability was examined using naturalistic data for 24 drivers. Driver inattention was placed into two categories based on whether drivers were looking forward toward the roadway (inattention with eyes-on-road) or not looking forward (inattention with eyes-off-road) while engaged in a secondary task. Repeated measures regression models were used to account for within-subject correlations. The results showed that, after accounting for driving speed and lane width, the eyes-off-road significantly increased the standard deviation of lane position (SDLP). The findings from this study are consistent with other studies that show that the amount of time drivers spend looking away from the road can impact drivers' ability to maintain their lane position. Additionally, this paper demonstrates how driver inattention can be examined with real world data while accounting for the roadway, environment, and driver behavior.

Crash risk factors related to individuals sustaining and drivers following traumatic brain injuries

OBJECTIVE

Some crashes result in drivers experiencing (or sustaining) a traumatic brain injury (TBI) while other crashes involve drivers that have already experienced a TBI. The objective of this study is to examine the factors that influence these two TBI crash groups.

METHODS

Data from the Iowa Department of Public Health's Brain Injury Registry and Department of Transportation's crash records were linked together and used in logistic regression models to predict the likelihood of a driver sustaining a TBI in a crash and those who drive after a TBI.

RESULTS

Between 2001 and 2006, there were 2382 crashes in which an individual sustained a TBI. As expected, a higher likelihood of sustaining a TBI was observed for motorcycle drivers who did not wear a helmet and in crashes that resulted in total or disabling vehicle damage. Focusing specifically on the post-TBI drivers (and not occupants), 1583 were involved in crashes. These post-TBI drivers were less likely to wear seatbelts or have passengers in the vehicle at the time of the crash, and were more likely to crash at night. Post-TBI drivers were also involved in significantly more multiple crashes (about 14%) when compared to drivers who have not experienced a TBI (about 10%) during the study period. When controlling for gender, date of injury, and severity of TBI (using Glasgow Coma Scale), individuals that sustained a TBI when they were younger were more likely to be involved in multiple crashes.

CONCLUSIONS

Different factors influence the crash likelihood for those that sustain a TBI in a crash and those that crash following a TBI. In general, post-TBI drivers have a higher occurrence of multiple crashes and this should be further explored to guide driver rehabilitation, evaluation, and training.

Use patterns among early adopters of adaptive cruise control

OBJECTIVE

The objective of this study was to investigate use patterns among early adopters of adaptive cruise control (ACC).

BACKGROUND

Extended use ofACC may influence a driver's behavior in the long-term, which can have unintended safety consequences.

METHOD

The authors examined the use of a motion-based simulator by 24 participants (15 males and 9 females). Cluster analysis was performed on drivers' use of ACC and was based on their gap settings, speed settings, number of warnings issued, and ACC disengaged. The data were then examined on the basis of driving performance measures and drivers' subjective responses to trust in ACC, understanding of system operations, and driving styles. Driving performance measures included minimum time headway, adjusted minimum time to collision, and drivers' reaction time to critical events.

RESULTS

Three groups of drivers were observed on the basis of risky behavior, moderately risky behavior, and conservative behavior. Drivers in the conservative group stayed farther behind the lead vehicle than did drivers in the other two groups. Risky drivers responded later to critical events and had more ACC warnings issued.

CONCLUSION

Safety consequences with ACC may be more prevalent in some driver groups than others. The findings suggest that these safety implications are related to trust in automation, driving styles, understanding of system operations, and personalities.

APPLICATION

Potential applications of this research include enhanced design for next-generation ACC systems and countermeasures to improve safe driving with ACC.

Augmenting the Technology Acceptance Model with Trust: Commercial Drivers’ Attitudes towards Monitoring and Feedback

This study evaluates truck drivers’ attitudes toward an on-board monitoring system (OBMS), using an extended version of the Technology Acceptance Model (TAM) that accounts for drivers’ trust in OBMS. Crashes that involve trucks incur a high cost to society and driver-related factors contribute to about one third of all large truck fatal crashes in the US. Therefore, safety initiatives that can increase drivers’ awareness of their risky behaviors are highly desirable. In-vehicle feedback systems are designed to serve this purpose; however, their benefits will not be realized unless their information can positively influence safe driving. Acceptance constructs for the proposed model were measured using a survey administered after the monitoring system was introduced to the drivers but before the system was actually installed in their trucks. In line with the TAM, the results demonstrated that perceived usefulness is the most important determinant of intention to use the OBMS. Trust was also a major determinant of intention to use, suggesting that the acceptance model can be usefully augmented by this construct.

Using driving simulators to assess driving safety

Changes in drivers, vehicles, and roadways pose substantial challenges to the transportation safety community. Crash records and naturalistic driving data are useful for examining the influence of past or existing technology on drivers, and the associations between risk factors and crashes. However, they are limited because causation cannot be established and technology not yet installed in production vehicles cannot be assessed. Driving simulators have become an increasingly widespread tool to understand evolving and novel technologies. The ability to manipulate independent variables in a randomized, controlled setting also provides the added benefit of identifying causal links. This paper introduces a special issue on simulator-based safety studies. The special issue comprises 25 papers that demonstrate the use of driving simulators to address pressing transportation safety problems and includes topics as diverse as neurological dysfunction, work zone design, and driver distraction.

Drivers' Understanding of Adaptive Cruise Control Limitations

Adaptive cruise control (ACC) is one system that is changing the driver-vehicle relationship. However, not all drivers are aware of the systems' capabilities or limitations. In this study, a cluster analysis was used to classify drivers based on how aware they were of the limitations associated with ACC. Three cluster groups emerged: those who are aware, unaware, and unsure of ACC limitations. Further examination revealed that drivers who were unaware or unsure exhibited potentially hazardous behavior when compared to the aware group. These two groups were more willing to use ACC when tired or on curvy roads. The unaware and unsure groups were also more likely to use conventional cruise control (CCC) in the absence of ACC. All three cluster groups reported high levels of trust in ACC. This may be problematic for the unaware and unsure groups since they may trust the system based on inappropriate expectations which can impact driver safety. Lower levels of awareness coupled with high levels of trust in ACC may correspond to potential misuse of the system. However, the findings suggest that this could be potentially mitigated through extended use of ACC.

The interaction of cognitive load and attention-directing cues in driving

OBJECTIVE

This study investigated the effect of a nondriving cognitively loading task on the relationship between drivers' endogenous and exogenous control of attention.

BACKGROUND

Previous studies have shown that cognitive load leads to a withdrawal of attention from the forward scene and a narrowed field of view, which impairs hazard detection.

METHOD

Posner's cue-target paradigm was modified to study how endogenous and exogenous cues interact with cognitive load to influence drivers' attention in a complex dynamic situation. In a driving simulator, pedestrian crossing signs that predicted the spatial location of pedestrians acted as endogenous cues. To impose cognitive load on drivers, we had them perform an auditory task that simulated the demands of emerging in-vehicle technology. Irrelevant exogenous cues were added to half of the experimental drives by including scene clutter.

RESULTS

The validity of endogenous cues influenced how drivers scanned for pedestrian targets. Cognitive load delayed drivers' responses, and scene clutter reduced drivers' fixation durations to pedestrians. Cognitive load diminished the influence of exogenous cues to attract attention to irrelevant areas, and drivers were more affected by scene clutter when the endogenous cues were invalid.

CONCLUSION

Cognitive load suppresses interference from irrelevant exogenous cues and delays endogenous orienting of attention in driving.

APPLICATION

The complexity of everyday tasks, such as driving, is better captured experimentally in paradigms that represent the interactive nature of attention and processing load.

Age-related differences in visual scanning at median-divided highway intersections in rural areas

The objective of this study was to examine age-related differences in visual scanning as drivers performed three separate maneuvers (going straight across, making a left and right turn) at two median-divided highway intersections with different crash frequencies. An on-road study was conducted with 60 drivers in three age groups: younger (18-25), middle-aged (35-55), and older (65-80). The study consisted of two between-subject (age and gender) and two within-subject variables (drive maneuver and intersection type). Drivers' behavior was measured by the proportion of time they visually sampled towards the left, right and rearview mirror, and by an entropy rate representative of randomness in visual scanning. The results showed that older and younger drivers do not utilize their full scanning range when compared to middle-aged drivers, as indicated by lower entropy rate and the tendency to check fewer areas before executing a maneuver through the intersections. This trend was more obvious during left and right turn maneuvers indicating a greater likelihood to miss an unexpected event. Older drivers had a significantly smaller proportion of visual sampling to the left and right during intersection negotiations when compared to younger and middle-aged drivers. Older and younger drivers checked the rearview mirror significantly less when compared to middle-aged drivers.

The Iowa Graduated Driver Licensing program: effectiveness in reducing crashes of teenage drivers

PROBLEM

Graduated Driver Licensing (GDL) programs vary in the United States in terms of implementation and restrictions. The State of Iowa's GDL program is assessed for its effectiveness in reducing crashes among teenage drivers.

METHOD

Time series analysis was used to evaluate police documented crashes involving 16-, 17-, and 18-year-old drivers over a 10 year period, with an intervention identified at the point of GDL implementation.

RESULTS

After controlling for seasonal trends and auto-correlative effects, a significant reduction in the crash rate of and 16- and 17-year-old drivers was observed due to the GDL implementation. However, there were no significant reductions in crash rates for 18-year-old drivers.

DISCUSSION

The analyses suggest that the Iowa GDL program is effective in reducing the crash rates of 16- and 17-year-old drivers but the effects do not sustain for 18-year-old drivers.

IMPACT ON INDUSTRY

The results suggest that the program appears to be working, however further analysis is needed to determine what factors are preventing lasting effects for these teenage drivers.

Driver Performance in the Moments Surrounding a Microsleep

This study examined if individuals who are at increased risk for drowsy-driving because of obstructive sleep apnea syndrome (OSAS), have impairments in driving performance in the moments during microsleep episodes as opposed to during periods of wakefulness. Twenty-four licensed drivers diagnosed with OSAS based on standard clinical and polysomnographic criteria, participated in an hour-long drive in a high-fidelity driving simulator with synchronous electroencephalographic (EEG) recordings for identification of microsleeps. The drivers showed significant deterioration in vehicle control during the microsleep episodes compared to driving performance in the absence of microsleeps on equivalent segments of roadway. The degree of performance decrement correlated with microsleep duration, particularly on curved roads. Results indicate that driving performance deteriorates during microsleep episodes. Detecting microsleeps in real-time and identifying how these episodes of transition between wakefulness and sleep impair driver performance is relevant to the design and implementation of countermeasures such as drowsy driver detection and alerting systems that use EEG technology.

Mitigating driver distraction with retrospective and concurrent feedback

OBJECTIVES

An experiment was conducted to assess the effects of retrospective and combined retrospective and concurrent feedback on driver performance and engagement in distracting activities.

BACKGROUND

A previous study conducted by the authors showed that concurrent (or real time) feedback can help drivers better modulate their distracting activities. However, research also shows that concurrent feedback can pose additional distractions due to the limited time and resources available during driving. Retrospective feedback, which is presented at the end of a trip (i.e., post-drive), can include additional information on safety critical situations during a trip and help the driver learn safe driving habits.

METHOD

A driving simulator study was conducted with 48 participants and 3 conditions: retrospective feedback, combined feedback (both retrospective and concurrent), and no feedback (baseline case).

RESULTS

The feedback conditions (retrospective and combined) resulted in faster response to lead vehicle braking events as depicted by shorter accelerator release times. Moreover, combined feedback also resulted in longer glances to the road.

CONCLUSIONS

The results suggest that both feedback types have potential to improve immediate driving performance and driver engagement in distractions.

APPLICATION

Combined feedback holds the most promise for mitigating the effects of distraction from in-vehicle information systems.

The influence of driver distraction on the severity of injuries sustained by teenage drivers and their passengers

Studies show that teenage drivers are at a higher risk for crashes. Opportunities to engage in technology and non-technology based distractions appear to be a particular concern among this age group. An ordered logit model was developed to predict the likelihood of a severe injury for these drivers and their passenger using a national crash database (the 2003, U.S. DOT-General Estimate System [GES]). As one would expect, speeding substantially increases the likelihood of severe injuries for teenage drivers and their passengers. The results of the analysis also reveal that teenage drivers have an increased likelihood of more severe injuries if distracted by a cell phone or by passengers than if the source of distraction was related to in-vehicle devices or if the driver was inattentive. Additionally, passengers of teenage drivers are more likely to sustain severe injuries when their driver is distracted by devices or passengers than with a non-distracted or inattentive driver. This supports the previous literature on teenage drivers and extends our understanding of injuries for this age group related to distraction-related crashes.

Cyanobacterial ecology across environmental gradients and spatial scales in China's hot and cold deserts

Lithic photoautotrophic communities function as principal primary producers in the world's driest deserts, yet many aspects of their ecology remain unknown. This is particularly true for Asia, where some of the Earth's oldest and driest deserts occur. Using methods derived from plant landscape ecology, we measured the abundance and spatial distribution of cyanobacterial colonization on quartz stony pavement across environmental gradients of rainfall and temperature in the isolated Taklimakan and Qaidam Basin deserts of western China. Colonization within available habitat ranged from 0.37+/-0.16% to 12.6+/-1.8%, with cold dry desert sites exhibiting the lowest abundance. Variation between sites was most strongly correlated with moisture-related variables and was independent of substrate availability. Cyanobacterial communities were spatially aggregated at multiple scales in patterns distinct from the underlying rock pattern. Site-level differences in cyanobacterial spatial pattern (e.g. mean inter-patch distance) were linked with rainfall, whereas patchiness within sites was correlated with local geology (greater colonization frequency of large rocks) and biology (dispersal during rainfall). We suggest that cyanobacterial patchiness may also in part be self-organized - that is, an outcome of soil water-biological feedbacks. We propose that landscape ecology concepts and models linking desert vegetation, biological feedbacks and ecohydrological processes are applicable to microbial communities.

Visual attention in driving: the effects of cognitive load and visual disruption

OBJECTIVE

This study investigates the effect of cognitive load on guidance of visual attention.

BACKGROUND

Previous studies have shown that cognitive load can undermine driving performance, particularly drivers' ability to detect safety-critical events. Cognitive load combined with the loss of exogenous cues, which can occur when the driver briefly glances away from the roadway, may be particularly detrimental.

METHOD

In each of two experiments, twelve participants engaged in an auditory task while performing a change detection task. A change blindness paradigm was implemented to mask exogenous cues by periodically blanking the screen in a driving simulator while a change occurred. Performance measures included participants' sensitivity to vehicle changes and confidence in detecting them.

RESULTS

Cognitive load uniformly diminished participants' sensitivity and confidence, independent of safety relevance or lack of exogenous cues. Periodic blanking, which simulated glances away from the road-way, undermined change detection to a greater degree than did cognitive load; however, drivers' confidence in their ability to detect changes was diminished more by cognitive load than by periodic blanking.

CONCLUSION

Cognitive load and short glances away from the road are additive in their tendency to increase the likelihood of drivers missing safety-critical events.

APPLICATION

This study demonstrates the need to consider the combined consequence of cognitive load and brief glances away from the road in the design of emerging in-vehicle devices and the need to provide drivers with better feedback regarding these consequences.