High risk of near-crash driving events following night-shift work

ABSTRACT

Night-shift workers are at high risk of drowsiness-related motor vehicle crashes as a result of circadian disruption and sleep restriction. However, the impact of actual night-shift work on measures of drowsiness and driving performance while operating a real motor vehicle remains unknown.

Sixteen night-shift workers completed two 2-h daytime driving sessions on a closed driving track at the Liberty Mutual Research Institute for Safety: (i) a postsleep baseline driving session after an average of 7.6 ± 2.4 h sleep the previous night with no night-shift work, and (ii) a postnight-shift driving session following night-shift work. Physiological measures of drowsiness were collected, including infrared reflectance oculography, electroencephalography, and electrooculography. Driving performance measures included lane excursions, near-crash events, and drives terminated because of failure to maintain control of the vehicle.

Eleven near-crashes occurred in 6 of 16 postnight-shift drives (37.5%), and 7 of 16 postnight-shift drives (43.8%) were terminated early for safety reasons, compared with zero near-crashes or early drive terminations during 16 postsleep drives (Fishers exact: P = 0.0088 and P = 0.0034, respectively). Participants had a significantly higher rate of lane excursions, average Johns Drowsiness Scale, blink duration, and number of slow eye movements during postnight-shift drives compared with postsleep drives (3.09/min vs. 1.49/min; 1.71 vs. 0.97; 125 ms vs. 100 ms; 35.8 vs. 19.1; respectively, P < 0.05 for all).

Night-shift work increases driver drowsiness, degrading driving performance and increasing the risk of near-crash drive events. With more than 9.5 million Americans working overnight or rotating shifts and one-third of United States commutes exceeding 30 min, these results have implications for traffic and occupational safety.

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From the full-text paper:

This was a driving study on a closed track following night-shift work vs following a standard night sleep. A driving instructor sat in the vehicle for safety purposes.
In alignment with real accident data, these findings “indicate that prolonged driving may be especially hazardous during the homeward commute following night-shift work” (p177).
All of the emergency near crash events (when the safety instructor in the vehicle intervened to stop the vehicle) and drive terminations occurred in the post nightshift drive condition – none of these events occurred in the post-sleep drive condition.
Nearly 40% of the post night-shift daytime drives required the use of emergency braking manoeuvres for near-crash driving events vs. 0% in the post-sleep condition.
They found “a substantially increased risk of objectively measured drowsiness, impaired driving performance, and critical driving incidents when driving during the daytime following a night shift in actual night-shift workers” (p178).
Drivers in the post night-shift condition frequently exhibited indicators of drowsiness that worsened as the drive progressed (e.g. increases in blink duration, frequency of slow eye movements, attentional failures, microsleep episodes). Time-on-task fatigue effects appeared to have interacted with night-shift work.
While the most severe objective driving impairments were observed after the 45 minute mark, concerningly objective impairments in driving were observed from as early as 15 minutes into the drives.
That is, “deficits in driving performance outcomes (lane crossings) and physiological measures indicative of drowsiness were also evident from the outset of the drive, indicating that impairment among these night-shift workers occurred within the first 15 min of postnight-shift driving” (p180).
It’s worth noting however that simulator studies (on high-fidelity computer simulations) and closed track studies (like this one) may amplify the effects of objective driving impairment and also sleep-related physiological effects because real-world open road drives may be more stimulating, compared to closed tracks which are geometrically simpler and with less stimulations to navigate.

Authors: Lee, M. L., Howard, M. E., Horrey, W. J., Liang, Y., Anderson, C., Shreeve, M. S., … & Czeisler, C. A. (2016). Proceedings of the National Academy of Sciences, 113(1), 176-181.

Study link: www.pnas.org/cgi/doi/10.1073/pnas.1510383112

Link to the LinkedIn article: https://www.linkedin.com/pulse/high-risk-near-crash-driving-events-following-work-ben-hutchinson