title: Naturalistic field study of the restart break in US commercial motor vehicle drivers: Truck driving, sleep, and fatigue.
abstract: Commercial motor vehicle (CMV) drivers in the US may start a new duty cycle after taking a 34-h restart break. A restart break provides an opportunity for sleep recuperation to help prevent the build-up of fatigue across duty cycles. However, the effectiveness of a restart break may depend on its timing, and on how many nighttime opportunities for sleep it contains. For daytime drivers, a 34-h restart break automatically includes two nighttime periods. For nighttime drivers, who are arguably at increased risk of fatigue, a 34-h restart break contains only one nighttime period. To what extent this is relevant for fatigue depends in part on whether nighttime drivers revert back to a nighttime-oriented sleep schedule during the restart break. We conducted a naturalistic field study with 106 CMV drivers working their normal schedules and performing their normal duties. These drivers were studied during two duty cycles and during the intervening restart break. They provided a total of 1260days of data and drove a total of 414,937 miles during the study. Their duty logs were used to identify the periods when they were on duty and when they were driving and to determine their duty cycles and restart breaks. Sleep/wake patterns were measured continuously by means of wrist actigraphy. Fatigue was assessed three times per day by means of a brief psychomotor vigilance test (PVT-B) and a subjective sleepiness scale. Data from a truck-based lane tracking and data acquisition system were used to compute lane deviation (variability in lateral lane position). Statistical analyses focused on 24-h patterns of duty, driving, sleep, PVT-B performance, subjective sleepiness, and lane deviation. Duty cycles preceded by a restart break containing only one nighttime period (defined as 01:00-05:00) were compared with duty cycles preceded by a restart break containing more than one nighttime period. During duty cycles preceded by a restart break with only one nighttime period, drivers showed more nighttime-oriented duty and driving patterns and more daytime-oriented sleep patterns than during duty cycles preceded by a restart break with more than one nighttime period. During duty cycles preceded by a restart break with only one nighttime period, drivers also experienced more lapses of attention on the PVT-B and increased lane deviation at night, and they reported greater subjective sleepiness. Importantly, drivers exhibited a predominantly nighttime-oriented sleep schedule during the restart break, regardless of whether the restart break contained only one or more than one nighttime period. Consistent with findings in laboratory-based studies of the restart break, the results of this naturalistic field study indicate that having at least two nighttime periods in the restart break provides greater opportunity for sleep recuperation and helps to mitigate fatigue.
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, P.O. Box 1495, Spokane, WA 99224, USA. Electronic address: amy.sparrow@wsu.edu.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Sparrow
authors.affiliation: Pulsar Informatics, Inc., 3401 Market Street, Suite 318, Philadelphia, PA 19104, USA. Electronic address: daniel@pulsarinformatics.com.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Mollicone
authors.affiliation: Pulsar Informatics, Inc., 3401 Market Street, Suite 318, Philadelphia, PA 19104, USA. Electronic address: kkan@pulsarinformatics.com.
authors.forename: Kevin
authors.initials: K
authors.lastname: Kan
authors.affiliation: Pulsar Informatics, Inc., 3401 Market Street, Suite 318, Philadelphia, PA 19104, USA. Electronic address: rbartels05@gmail.com.
authors.forename: Rachel
authors.initials: R
authors.lastname: Bartels
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, P.O. Box 1495, Spokane, WA 99224, USA. Electronic address: satterfield@vetmed.wsu.edu.
authors.forename: Brieann C
authors.initials: BC
authors.lastname: Satterfield
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, P.O. Box 1495, Spokane, WA 99224, USA. Electronic address: samantha.riedy@wsu.edu.
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Riedy
authors.affiliation: Pulsar Informatics, Inc., 3401 Market Street, Suite 318, Philadelphia, PA 19104, USA. Electronic address: aaron@pulsarinformatics.com.
authors.forename: Aaron
authors.initials: A
authors.lastname: Unice
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, P.O. Box 1495, Spokane, WA 99224, USA. Electronic address: hvd@wsu.edu.
authors.forename: Hans P A
authors.initials: HPA
authors.lastname: Van Dongen
mesh_terms: D000328:Adult; D000368:Aged; D001288:Attention; D001334:Automobile Driving / Q000523:psychology*; D005221:Fatigue; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018986:Motor Vehicles; D011597:Psychomotor Performance; D012308:Risk Management / Q000379:methods*; D012890:Sleep / Q000502:physiology*; D013997:Time Factors; D014481:United States; D000066477:Work Performance / Q000706:statistics & numerical data; D014940:Work Schedule Tolerance; D055815:Young Adult
keywords: Circadian rhythm; Drowsy driving; Fatigue risk management; Hours of service; Recovery sleep; Recycling