The efficacy of putative ''in-car'' countermeasures to driver sleepine
ss is unknown. Sixteen young adult drivers within the normal range for
the Epworth Sleepiness Scale (ESS), had their sleep restricted to 5 h
ours the night before, and drove an interactive car simulator in the a
fternoon for 2.5 hours, under monotonous conditions. After 30 minutes
of driving they were exposed to: (1) cold air to the face (AIR) from t
he vehicle's air conditioning vents, (2) listening to the vehicle's ra
dio/tape (RADIO) according to subjects' choice, or (3) NIL treatment.
The active treatments typified those experienced under real driving co
nditions. Drifting over lane markings were ''incidents,'' EEGs were re
corded and spectrally analyzed in the alpha and theta range. Subjects
responded to the Karolinska Sleepiness Scale (KSS) every 200 seconds.
Overall, RADIO and AIR had no significant effects on incidents, althou
gh there was a trend for RADIO to reduce incidents, particularly durin
g the first 30 minutes, when AIR also had some effect. KSS scores were
significantly lower for RADIO for most of the drive, whereas AIR had
only transient and non-significant effects. The EEG showed no signific
ant effects of the active treatments. Compared with other countermeasu
res such as caffeine and a brief nap, which we have previously shown t
o be more effective (using the same equipment and protocols), AIR and
RADIO are at best only temporary expedients to reduce driver sleepines
s, perhaps enabling drivers to find a suitable place to stop, take a b
reak and avail themselves of caffeine and a nap.