Evaluation "in-car" countermeasures to sleepiness: cold air and radio.

The efficacy of putative "in-car" countermeasures to driver sleepiness is unknown. Sixteen young adult drivers within the normal range for the Epworth Sleepiness Scale (ESS), had their sleep restricted to 5 hours the night before, and drove an interactive car simulator in the afternoon for 2.5 hours, under monotonous conditions. After 30 minutes of driving they were exposed to: (1) cold air to the face (AIR) from the vehicle's air conditioning vents, (2) listening to the vehicle's radio/tape (RADIO) according to subjects' choice, or (3) NIL treatment. The active treatments typified those experienced under real driving conditions. Drifting over lane markings were "incidents." EEGs were recorded 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, although there was a trend for RADIO to reduce incidents, particularly during 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 significant effects of the active treatments. Compared with other countermeasures such as caffeine and a brief nap, which we have previously shown to be more effective (using the same equipment and protocols), AIR and RADIO are at best only temporary expedients to reduce driver sleepiness, perhaps enabling drivers to find a suitable place to stop, take a break and avail themselves of caffeine and a nap.