Field Study on the Efficacy of the New Restart Provision for Hours of Service [Research Brief]

NHTSA · 2014 · ROSA P / United States. Federal Motor Carrier Safety Administration

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Summary

This research brief summarizes a naturalistic field study sponsored by the Federal Motor Carrier Safety Administration (FMCSA) to evaluate the efficacy of the "restart provision" within the Hours of Service of Drivers Final Rule. Published in December 2011 with a July 2013 compliance date, the rule mandates that commercial motor vehicle (CMV) drivers must include at least two nighttime periods (1 a.m. to 5 a.m.) in their restart breaks to reset their 60 or 70-hour duty-cycle limits. The study aimed to determine whether this requirement sufficiently promotes sleep recuperation and mitigates driver fatigue. The study involved 106 CMV drivers (100 men, 6 women; ages 24–69) with a mean of 12.4 years of driving experience. Researchers measured sleep and fatigue across two consecutive duty cycles and the intervening restart breaks without altering drivers’ normal schedules. Drivers were categorized into two conditions based on their preceding restart break: those with one nighttime period versus those with two or more nighttime periods. Fatigue was assessed objectively using a smartphone-administered Psychomotor Vigilance Test (PVT), where attention lapses were defined as reaction times exceeding 355 milliseconds, and subjectively through self-reported sleepiness. Key findings revealed significant differences between the two conditions. Drivers who experienced a restart break with only one nighttime period exhibited greater fatigue and poorer performance during subsequent duty cycles. Specifically, they showed more lapses of attention, particularly at night, and reported higher subjective sleepiness toward the end of their duty periods. These drivers also demonstrated increased lane deviation variability at night and in the morning and afternoon. Behaviorally, drivers in the one-nighttime-period condition predominantly drove and remained on duty at night, while sleeping primarily during the day. In contrast, drivers with two or more nighttime periods in their restart breaks distributed driving time more evenly across the day and slept predominantly at night during restart breaks. Although average sleep duration during duty cycles was similar (6.2 hours vs. 6.0 hours), the quality of recuperation differed; drivers with one nighttime period had 1.3 more attention lapses per PVT during restart breaks, indicating insufficient recovery. The study concludes that the requirement for at least two nighttime periods in restart breaks effectively mitigates fatigue, as evidenced by reduced attention lapses and lower subjective sleepiness. The results provide empirical support for the efficacy of the new restart rule, suggesting that the mandated break structure helps drivers recuperate sufficiently, thereby potentially reducing crash risk associated with fatigue-induced attention lapses.

Key finding

Drivers whose restart break contained only one nighttime period averaged 0.4 more attention lapses per 3-minute PVT overall and 0.8 more at night than drivers with two or more nighttime periods.

Methodology

naturalistic

Sample size: 106

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• truck driver fatigue
• hours of service
• shift work driving
• time on task
• circadian factors
• sleep deprivation

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: behavioral performance data