Driver Situation Awareness and Perceived Sleepiness during Truck Platoon Driving – Insights from Eye-tracking Data

Truck platoon driving technology uses vehicle-to-vehicle communication to allow one truck to follow another in an automated fashion. The first vehicle is operated manually, the second vehicle is driven semi-automatically once platoon-mode is activated. In this mode, the driver merely has to monitor traffic. Semi-automated driving in passenger cars has been shown to increase driver sleepiness and reduce situation awareness. The aim of the present study was to gain first insights whether this also applies to semi-automated platoon driving and whether platoon-specific situations pose special visual demands. In a first on-road experiment, ten professional truck drivers experienced a two-vehicle platooning system on a German highway as platoon follower or leader. In addition, all drivers conducted reference drives with a single truck. Driver situation awareness was measured with eye-tracking recordings, perceived sleepiness with subjective ratings. The results showed that the lead vehicle drivers kept their eyes less time on the road ahead as compared to normal truck driving. In particular in situations that required decoupling, drivers (in the lead vehicle as well as in the following vehicle) spent about 40% of fixations on the HMI. That is, situation awareness was reduced, amounting to potentially risky behavior, as the platoon goes blindfolded when both drivers attend to the display. Drivers did not report higher perceived sleepiness in semi-automated platoon drives than in the manual reference drives. Adequate solutions to reduce the time spent looking away from the road are required. Head-up displays should be investigated for this purpose, as they can simplify driver communication and present platoon-specific information while the eyes remain on the road.