Citation

Ranney T, Simmons L, Boulos Z, Macchi M. Transp. Res. Rec. 1999; 1686: 49-56.

Copyright

(Copyright © 1999, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/1686-08

PMID

unavailable

Abstract

Eight professional drivers completed two replications of a 2-day (43- to 47-h) protocol, each including 8 h of overnight driving following a truncated (5-h) sleep period on the previous night. One replication included a 3-h nap on the afternoon before the overnight driving. The overnight driving consisted of four 2-h runs separated by half-hour breaks. The driving task, conducted in a fixed-base heavy-truck simulator, included vehicle control on straight and curved roads, detection of pedestrians appearing alongside the roadway and of targets in the mirrors, and avoidance of obstacles and oncoming vehicles. The results indicated that extended overnight driving following a night of partial sleep restriction induced significant driving impairment. Specifically, crash frequencies increased over time, and the proportion of driving completed before the first crash decreased. Drivers detected fewer mirror targets and became slower in detecting pedestrian targets over time. The afternoon nap improved overall driving performance, as reflected by reductions in crash frequencies. On average, drivers completed 72 percent of each 2-h run without crashes in the nap condition, compared with 51 percent in the no-nap condition. Implications of napping as a fatigue countermeasure are discussed.