Commercial Motor Vehicle Driver Fatigue, Long-Term Health, and Highway Safety Research Needs (2016) / Chapter Skim
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7 Fatigue, Hours of Service, and Highway Safety
7 Fatigue, Hours of Service, and Highway Safety
Pages 107-130
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From page 107... ...
, and other improvements are being made in the design of trucks and buses, in the driving environment, possibly in commercial motor vehicle (CMV) drivers' personal habits, and in the scheduling poli cies of carriers.
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From page 108... ...
. After providing an introduction to crash risk due to fatigue, this chapter summarizes the techniques that have been used and the data sets to which they have been applied in some of the leading research on how increases in hours of service and increases in fatigue are linked to increases in crash risk for CMV drivers.
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From page 109... ...
Relative to driving a passenger vehicle, CMV driving often involves longer periods of continuous driving, greater fractions of a day and of a week spent driving, the resulting lifestyle, the economic pressures to continue driving when fatigued, the physical demands of loading and unloading, and the differences in driving a truck or bus compared with a passenger car, not to mention the lack of an analogue to HOS regulations. All of these factors contribute to the panel's view that the emphasis here should be on research on the relationship among fatigue, hours of service, and crash risk for CMV drivers.
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From page 110... ...
estimated that 1-4 percent of truck crashes were related to driver fatigue.) A more realistic estimate of the percentage of serious truck crashes linked to driver fatigue comes from the Large Truck Crash Causation Study (LTCCS)
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From page 111... ...
Clearly, this is an area in need of further research. RESEARCH ON FATIGUE, HOURS OF SERVICE, AND RISK OF COMMERCIAL MOTOR VEHICLE CRASHES Following are summaries and critiques of some of the key research examining the relationship among CMV driver fatigue, HOS regulations, and crash risk.
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From page 112... ...
The authors also found that a decrease in the quality of the steering raised crash risk. Fatigue, Alcohol, Other Drugs, and Medical Factors in Fatal-to-the-Driver Heavy Truck Crashes, Safety Study (National Transportation Safety Board, 1990)
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From page 113... ...
was "to observe and measure the development and progression of driver fatigue and loss of alertness, and to develop countermeasures to address it, through a field study.…" Beginning in 1993, 80 truck drivers aged 25-65 with at least 1 year of experience in the United States and Canada driving long-haul less-than-truckload cargo in tractor-semi-trailers were monitored for 16 weeks each as part of a naturalistic driving study. Data were collected on work-related factors "thought to influence the development of fatigue, loss of alertness, and degraded driving performance in commercial motor vehicle drivers." As is typical of naturalistic driving studies (see Chapter 5)
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From page 114... ...
The fact that there was more than one difference among the schedules confounded attempts to interpret comparisons of means across the four groups. Effects of Sleep Schedules on Commercial Motor Vehicle Driver Performance (Balkin et al., 2000)
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From page 115... ...
To employ the Stanford sleepiness scale, the researchers had respondents select one of seven statements that most closely described their alertness immediately before the crash. Controls were similarly interviewed around the time of their selection.
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From page 116... ...
In the Motor Carrier Safety Improvement Act of 1999, Congress mandated "a study to determine the causes of, and contributing factors to, crashes involving commercial motor vehicles." As a result, FMCSA and NHTSA conducted a "multiyear, nationwide study of factors that contribute to truck crashes.
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From page 117... ...
Work Schedules of Long-Distance Truck Drivers Before and After 2004 Hours-of-Service Rule Change (McCartt et al., 2008) 2 In this study, three samples of long-distance truck drivers were interviewed face to face as they passed through roadside weigh stations on Interstate highways in Pennsylvania and Oregon immediately before and after the 2003 change in the HOS regulations, which increased the limit on daily driving from 10 to 11 hours.
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From page 118... ...
This project was a naturalistic driving study of 98 CMV drivers (97 males, 1 female, age range of 24-60)
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From page 119... ...
In addition, there was evidence of a traffic-density effect. Investigation into Motor Carrier Practices to Achieve Optimal Commercial Motor Vehicle Driver Performance: Phase I (Von Dongen and Belenky, 2010)
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From page 120... ...
• Less-than-truckload data showed a pattern of increasing crash odds as driving time increased, with a consistent increase from hour 5 through hour 11. • Truckload data showed significant interactions between some multiday driving patterns and increased crash risk between the seventh and eleventh hours.
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From page 121... ...
on local and short-haul truck drivers to determine causes of fatigued driving. A major difference was that in the original analysis, attention was given only to safety-critical events.
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From page 122... ...
with an average of 9 years of experience driving commercial motor vehicles. The d rivers were employees of four for-hire trucking companies, and represented both long-haul operations and drivers that returned home most nights.
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From page 123... ...
Motorcoach Driver Fatigue Study, 2011 (Belenky et al., 2012) This study examined whether commercial motorcoach drivers were working within the limits set by the HOS regulations.
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From page 124... ...
The result was "an estimated 7.0 percent of all crashes in which a passenger vehicle was towed, 13.1 percent of crashes that resulted in a person being admitted to a hospital, and 16.5 percent of fatal crashes involved a drowsy driver." Drowsiness was determined on the basis of information from "interviews conducted by NASS CDS investigators with crash-involved occupants from police reports." The imputation used the following covariates: maximum injury, driver injury severity, number of vehicles in crash, pre-event maneuver, crash type, day of week, hour of day, traffic flow, number of passengers, driver age, driver gender, light condition, relation to intersection, roadway alignment, speed limit, number of lanes, surface conditions, precrash critical event, vehicle disposition, year, stratum, and primary sampling unit. Among crashes in which the driver was fatally injured, information on attention was missing for 92 percent.
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From page 125... ...
performed a meta-analysis of the impact of the use of continuous positive airway pressure (CPAP) treatment on motor vehicle crash risk for automobile and CMV drivers with OSA.
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From page 126... ...
(2002) Crash 1998-1999 Driver ratings of investigations, sleepiness; risk of interviews serious crash Federal Motor Carrier Crash 2001-2003 Fatal truck crash Safety Administration investigations, data, critical event (2006)
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From page 127... ...
FATIGUE, HOURS OF SERVICE, AND HIGHWAY SAFETY 127 Analyses Findings Caveats Logistic regression Driving in excess of 8 hours Driver fatigue measured case control results in a 1.8 times greater indirectly by time on task crash risk through logbook data Frequencies Fatigue cited as cause in 31 Driver fatigue assessed by percent of sample investigators' reconstruction Means, frequencies Time of day important; Confounded design drowsiness greatest during night driving Analysis of variance Both long- and short-haul Some driver populations drivers often get 7.5 hours of not subject to substantial sleep per 24 hours sleep loss Analysis of variance Driving triple trailers adds Small sample; many to fatigue possible confounders omitted Logistic regression Strong association between Much missing data; driver case control sleepiness and crash rate recall bias re sleep obtained Frequencies 7 to 13% of crashes Driver fatigue is assessed associated with sleep indirectly as critical events shortage at crash sites Frequencies, means Drivers reported more Interview self-reporting on sleep obtained under new fatigue HOS regulations; dozing increased with change in HOS regulations Frequencies, logistic First driving hour is most Some safety-critical events regression with risky; also time-of-day effect may not be evidence of generalized estimating and traffic density effect fatigue equations continued
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From page 128... ...
(2011) Company crash 2004-2005, Crash risk data 2010 Barr et al.
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From page 129... ...
FATIGUE, HOURS OF SERVICE, AND HIGHWAY SAFETY 129 Analyses Findings Caveats Frequencies, means 34-hour restart, day work Small sample size; many shift, nighttime sleep potential confounding effective at mitigating sleep factors loss, but work at night, sleep in day not so effective Odds ratios and Safety-critical events Combining safety-critical Poisson regression sometimes are effective events of different types surrogates, sometimes not may complicate inference Logistic regression Driving time was a Paper logs are of uncertain case control significant predictor of crash quality; no treatment of risk for less-than-truckload several confounding factors trucks Reanalysis of previous Fatigue associated with Small sample size; focus study; logistic young drivers, driving on local/short-haul truck regression case control between 6 and 9 AM, and drivers when starting out Frequencies, odds Rate of safety-critical events Small sample size; safetyratios, negative increases with time on task; critical events are uncertain binomial regression breaks are beneficial surrogates Means Motorcoach drivers function Mixed types of motorcoach well under current HOS drivers; no accounting for regulations some confounding factors Means Fatigue is affected by Small sample size circadian rhythms and by drive duration Frequencies 16.5% of fatal crashes Assessment of fatigue by involved a drowsy driver interview; much missing data
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From page 130... ...
: • Either more experimental control of important variables is neces sary for various confounding factors, or these factors need to be addressed after data collection using techniques such as propen sity scoring. • More research is needed on the relationship among HOS regula tions, driver fatigue, and crash risk for bus drivers.
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