Richard J. Hanowski

Commercial drivers' health: a naturalistic study of body mass index, fatigue, and involvement in safety-critical events.

Objective: To explore the relation of commercial truck drivers body mass indexex (BMI) to fatigued driving episodes and involvement in safety-critical events. Methods: One hundred and three professional truck drivers participated in a long-term naturalistic (on-road) driving study whereby vehicle motion data as well as video of the driver and driving environment were gathered continuously. This data set was analyzed to identify safety-critical events as well as fatigued driving episodes using two independent measures of fatigue. Odds ratio analyses were then performed to explore the relative risk of driving while fatigued and involvement in safety-critical events based on drivers BMI classification (obese versus non-obese). Results: Results indicated that of the 103 participating truck drivers, 53.4 percent were obese based on BMI. Odds ratio calculations revealed that obese individuals were between 1.22 (CI = 1.03–1.45) and 1.69 times (CI = 1.32–2.18) more likely than non-obese individuals to be rated as fatigued based on the two measures of fatigue. Other analyses showed that obese individuals were at 1.37 times (CI = 1.19–1.59) greater risk for involvement in a safety-critical event than non-obese individuals. Finally, one of the fatigue measures showed that obese individuals were 1.99 times (CI = 1.02–3.88) more likely than non-obese individuals to be fatigued while involved in an at-fault safety-critical incident. Conclusion: The results of this study support other research in the field of health and well-being that indicate a link between obesity and fatigue, which is a major safety issue surrounding commercial motor vehicle operations given the long hours these drivers spend on the road.

Commercial Driver Medical Examinations: Prevalence of Obesity, Comorbidities, and Certification Outcomes

Objective: The objective of this study was to assess relationships between body mass index (BMI) and comorbid conditions within a large sample of truck drivers. Methods: Commercial driver medical examination data from 88,246 commercial drivers between 2005 and 2012 were analyzed for associations between BMI, medical disorders, and driver certification. Results: Most drivers were obese (53.3%, BMI >30.0 kg/m2) and morbidly obese (26.6%, BMI >35.0 kg/m2), higher than prior reports. Obese drivers were less likely to be certified for 2 years and more likely to report heart disease, hypertension, diabetes mellitus, nervous disorders, sleep disorders, and chronic low back pain (all P < 0.0001). There are relationships between multiple potentially disqualifying conditions and increasing obesity (P < 0.0001). Morbid obesity prevalence increased 8.9% and prevalence of three or more multiple conditions increased fourfold between 2005 and 2012. Conclusions: Obesity is related to multiple medical factors as well as increasing numbers of conditions that limit driving certification.

An analysis of driving and working hour on commercial motor vehicle driver safety using naturalistic data collection

Current hours-of-service (HOS) regulations prescribe limits to commercial motor vehicle (CMV) drivers operating hours. By using naturalistic-data-collection, researchers were able to assess activities performed in the 14-h workday and the relationship between safety-critical events (SCEs) and driving hours, work hours, and breaks. The data used in the analyses were collected in the Naturalistic Truck Driving Study and included 97 drivers and about 735,000 miles of continuous driving data. An assessment of the drivers workday determined that, on average, drivers spent 66% of their shift driving, 23% in non-driving work, and 11% resting. Analyses evaluating the relationship between driving hours (i.e., driving only) and SCE risk found a time-on-task effect across hours, with no significant difference in safety outcomes between 11th driving hour and driving hours 8, 9 or 10. Analyses on work hours (i.e., driving in addition to non-driving work) found that risk of being involved in an SCE generally increased as work hours increased. This suggests that time-on-task effects may not be related to driving hours alone, but implies an interaction between driving hours and work hours: if a driver begins the day with several hours of non-driving work, followed by driving that goes deep into the 14-h workday, SCE risk was found to increase. Breaks from driving were found to be beneficial in reducing SCEs (during 1-h window after a break) and were effective in counteracting the negative effects of time-on-task.

The Risk of a Safety-Critical Event Associated With Mobile Device Use in Specific Driving Contexts

Objective: We explored drivers’ mobile device use and its associated risk of a safety-critical event (SCE) in specific driving contexts. Our premise was that the SCE risk associated with mobile device use increases when the driving task becomes demanding. Methods: Data from naturalistic driving studies involving commercial motor vehicle drivers and light vehicle drivers were partitioned into subsets representative of specific driving contexts. The subsets were generated using data set attributes that included level of service and relation to junction. These attributes were selected based on exogenous factors known to alter driving task demands. The subsets were analyzed using a case-cohort approach, which was selected to complement previous investigations of mobile device SCE risk using naturalistic driving data. Results: Both commercial motor vehicle and light vehicle drivers varied as to how much they conversed on a mobile device but did not vary their engagement in visual–manual subtasks. Furthermore, commercial motor vehicle drivers conversed less frequently as the driving task demands increased, whereas light vehicle drivers did not. The risk of an SCE associated with mobile device use was dependent on the subtask performed and the driving context. Only visual–manual subtasks were associated with an increased SCE risk, whereas conversing was associated with a decreased risk in some driving contexts. Conclusion: Drivers’ engagement in mobile device subtasks varies by driving context. The SCE risk associated with mobile device use is dependent on the types of subtasks performed and the driving context. The findings of this exploratory study can be applied to the design of driver–vehicle interfaces that mitigate distraction by preventing visual–manual subtasks while driving.

Efficacy of roll stability control and lane departure warning systems using carrier-collected data.

INTRODUCTIONnLarge truck crashes have significantly declined over the last 10 years, likely due, in part, to the increased use of onboard safety systems (OSS). Unfortunately, historically there is a paucity of data on the real-world efficacy of these devices in large trucks. The purpose of this study was to evaluate the two OSSs, lane departure warning (LDW) and roll stability control (RSC), using data collected from motor carriers.nnnMETHODnA retrospective cohort approach was used to assess the safety benefits of these OSSs installed on Class 7 and 8 trucks as they operated during normal revenue-producing deliveries. Data were collected from 14 carriers representing small, medium, and large carriers hauling a variety of commodities. The data consisted of a total of 88,112 crash records and 151,624 truck-years that traveled 13 billionmiles over the observation period.nnnRESULTSnThe non-LDW cohort had an LDW-related crash rate that was 1.917 times higher than the LDW cohort (p=0.001), and the non-RSC cohort had an RSC-related crash rate that was 1.555 times higher than the RSC cohort (p<0.001).nnnCONCLUSIONSnThe results across analyses indicated a strong, positive safety benefit for LDW and RSC under real-world conditions.nnnPRACTICAL APPLICATIONSnThe results support the use of LDW and RSC in reducing the crash types associated with each OSS.

Repeated Cross-Sectional Assessment of Commercial Truck Driver Health.

Objective: To assess relationships and trends over time in individual conditions and multiple conditions among a large sample of independent, nonoverlapping truck drivers using a repeated cross-sectional study design. Methods: Commercial driver medical examinations were conducted on 95,567 commercial drivers between January 1, 2005, and October 31, 2012. Specific medical conditions that have been identified by the Federal Motor Carrier Safety Administrations Medical Review Board as possibly increasing crash risk were examined. Prevalence and trends over time were analyzed. Results: A total of 8 of the 13 conditions significantly increased from 2005 to 2012. Prevalence of multiple concomitant conditions also increased, with prevalence odds ratios as high as 7.39 (95% confidence interval, 3.92 to 13.98) for four or more conditions in 2012 as compared with 2005. Conclusions: Individual and multiple conditions thought to be associated with increased crash risk significantly increased between 2005 and 2012.

Safety Benefits of Speed Limiters in Commercial Motor Vehicles Using Carrier-Collected Crash Data

The purpose of this study was to identify the safety impacts of speed limiters in commercial truck fleets. The primary safety analysis was a focus on the reduction in truck crashes that could have been avoided or mitigated with an active speed limiter installed on the truck. This was the first study to use actual truck crash data collected directly from commercial truck fleets, representing a wide array of crashes. The study included data from 20 commercial truck fleets, including approximately 138,000 truck-years and more than 15,000 truck crashes, as they operated under real-world, revenue-producing deliveries. The findings showed strong positive benefits for speed limiters. Results indicated that trucks equipped without speed limiters had a significantly higher speed limiter-relevant crash rate (approximately 200%) compared to trucks with speed limiters. The cost of the technology is negligible and would not be expected to be cost-prohibitive for commercial truck fleets/owners. The current study went further than any prior research conducted in this domain and provides important data on the efficacy of speed limiters in reducing speed limiter-relevant crashes.

A retrospective analysis of cardiometabolic health in a large cohort of truck drivers compared to the American working population

BACKGROUNDnTruck drivers face many health challenges, including lifestyle, diet, inactivity, stressors, and social support.nnnMETHODSnA repeated cross-sectional analysis compared 88,246 truck drivers with data from (nu2009=u200911u2009918) the National Health and Nutrition Examination Survey (NHANES). Trends over time for body mass index (BMI), high blood pressure, diabetes mellitus, heart disease, and sleep disorders were analyzed, adjusting for potential confounders.nnnRESULTSnTruck drivers had significantly worsening health metrics between 2005 and 2012 compared to NHANES participants. Truck drivers were significantly more likely to be obese and morbidly obese with prevalence odds ratios (POR) and 95% confidence intervals (95%CI) of 1.99 (1.87, 2.13) and 2.34 (2.16, 2.54), respectively. Measured blood pressure, self-reported high blood pressure, diabetes mellitus, and heart disease all significantly increased. Also, sleep disorders increased among truck drivers from 2005 to 2012 (PORu2009=u20096.55, 95%CI 5.68, 7.55).nnnCONCLUSIONnThese data suggest disproportionate increases in poor health among truck drivers from 2005 to 2012.

Multiple Conditions Increase Preventable Crash Risks among Truck Drivers in a Cohort Study

Objective: This study aims to quantify the crash risk for truck drivers with multiple comorbid medical conditions, after adjusting for confounders. Methods: This retrospective cohort of 38,184 drivers evaluated concomitant medical conditions and subsequent crash data between January 1, 2005, and October 31, 2012. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated for any cause and preventable crashes of varying severity. Results: Drivers with three or more medical conditions had a significantly increased risk of preventable Department of Transportation (DOT) reportable crashes (HRu200a=u200a2.53, 95% CIu200a=u200a1.65 to 3.88) and preventable crashes with injuries (HRu200a=u200a2.23, 95% CIu200a=u200a1.09 to 5.31) after adjustment for covariates. Similarly, adjusted HRs were 2.55 (95% CIu200a=u200a1.37 to 4.73) for any cause DOT-reportable crashes and 3.21 (95% CIu200a=u200a1.18 to 8.75) for any cause crashes with injuries. Conclusions: Having three concomitant medical conditions may be a statistically significant risk factor for preventable and any cause DOT-reportable crashes and crashes with injuries.

Data and methods for studying commercial motor vehicle driver fatigue, highway safety and long-term driver health

This article summarizes the recommendations on data and methodology issues for studying commercial motor vehicle driver fatigue of a National Academies of Sciences, Engineering, and Medicine study. A framework is provided that identifies the various factors affecting driver fatigue and relating driver fatigue to crash risk and long-term driver health. The relevant factors include characteristics of the driver, vehicle, carrier and environment. Limitations of existing data are considered and potential sources of additional data described. Statistical methods that can be used to improve understanding of the relevant relationships from observational data are also described. The recommendations for enhanced data collection and the use of modern statistical methods for causal inference have the potential to enhance our understanding of the relationship of fatigue to highway safety and to long-term driver health.