Karrer et al  let a representative sample of 83 German drivers perform for 2 hours on a monotonous driving task on motorway. Trained observers registered the occurrence of DWA, as being indicated by one or more of the following symptoms:
- The driver began to stare into space
- The drivers began to stare and head shakes upwards or downwards
- Start of rolling eye movement of the driver
- Start of squinting.
During the drive, the EEG (duration and frequency alpha waves), eye jumps (saccades) and the frequency of eye blinks were measured. Also, traffic errors were measured (mainly crossing over edge markings). DWA occurred for 18% of the drivers, and relatively more for young male drivers. The 83 participants in total crossed 260 times edge marking. In 33, 5% of these cases, DWA was present. DWA went together with a decrease in the number of eye jumps and a decrease in the size of the jumps. The higher the frequency of DWA moments, the longer the duration of eye blinks. This last results supports the conclusion that DWA occurs at a low intensity attention level and that this causes more traffic errors to be made.