Effects of an afternoon nap on nighttime alertness and performance in long-haul drivers

  • Published: Accident Analysis & Prevention. Volume 34, Issue 6, November 2002, Pages 825–834 (2002)
  • Authors: Macchia, M.M., Boulosa, Z., Ranneyb, T., Simmonsc, L. & Campbella, S.S.
  • Date Added: 29 Dec 2013
  • Last Update: 29 Dec 2013
  • Format: pdf


Measure the impact of naps on alertness and performance.


The effects of an afternoon nap on alertness and psychomotor performance were assessed during a simulated night shift. After a night of partial sleep restriction, eight professional long-haul drivers either slept (nap condition) or engaged in sedentary activities (no-nap condition) from 14:00 to 17:00 h. Alertness and performance testing sessions were conducted at 12:00 (pre-nap baseline), 24:00, 02:30, 05:00 and 07:30 h, and followed 2-h runs in a driving simulator.

Key Findings:

  • In the nap condition, the subjects showed lower subjective sleepiness and fatigue, as measured by visual analog scales, and faster reaction times and less variability on psychomotor performance tasks.

  • Electrophysiological indices of arousal during the driving runs also reflected the beneficial effects of the afternoon nap, with lower spectral activity in the theta (4–7.75 Hz), alpha (8–11.75 Hz) and fast theta-slow alpha (6–9.75 Hz) frequency bands of the electroencephalogram, indicating higher arousal levels.

  • Thus, a 3-hour napping opportunity ending at 17:00 improved significantly several indices of alertness and performance measured 7–14 hours later.


Nap, night shift, sleepiness, quantitative EEG, driving, driving simulator, performance


This research has far reaching positive impacts for night time truck drivers, showing that a 3 hour afternoon nap can improve their performance significantly when driving at night.