Sleepiness in professional truck drivers measured with an objective alertness test during routine traffic controls

Accurate data about sleepiness in professional drivers at the wheel are rare because it is difficult to perform objective and reliable sleepiness tests in the field. In this pilot study, we investigate the practicability, robustness and viability of the pupillographic sleepiness test (PST, F2D by Amtech GmbH, Germany) during routine police controls. PST analyses and quantifies the so-called sleepiness waves, spontaneous pupillary movements in the dark.

PST was recorded in 137 truck drivers, who were redirected by the police out of the freeway traffic to a service station for a spot check of their trip recorder, load and papers. Participation in the sleepiness test was voluntarily. The drivers' subjective sleepiness was determined with two questionnaires, the Stanford Sleepiness Scale (SSS) and the Epworth Sleepiness Scale (ESS). The PST provides the pupillary unrest index (PUI), which describes the magnitude of the spontaneous oscillation of the pupil. The PUI values within 1 standard deviation are classified as normal, between 1 and 2 SD as borderline and above 2 SD as sleepy.

The net examination time for the PST was 11 min, allowing it to be performed within the time required for the police to perform their control of load, truck and papers. In 126 truck drivers, the data sets were complete and of sufficient quality and could be evaluated (92%). Values of PUI more than 2 SDs were detected in 5.6% of drivers, whereas 72.2% were classified as normal and alert and 22.2% as borderline. The correlation of the PST score with the SSS score (p = 0.064) borders on significance, whereas no correlation could be found in comparison with ESS.

Sleepiness in drivers, assessed by the PST, can be tested during routine police controls. The results of this study show comparable values to those previously published, confirming the robustness and technical practicability of the method. Nevertheless, there is strong need for further evaluation of PST and its relation to driving performance. For justifiable values similar to the development of the drunk-driving law, there are detailed investigations needed.