Fig. 1. Light source and photodetector circuit

Fig. 2. Light source and detector probe

Fig. 3. Light source and detector arrangement and light source driving sequence

Fig. 4. Process of spaced cognitive experiments

Fig. 5. Data processing procedure

Fig. 6. The fatigue experiment process of the simulated driving test subjects

Fig. 7. Driving simulation experiment

Fig. 8. Subjects’ mean HbO change during the trial and accident statistics during driving

Fig. 9. HbO concentration changes for subject C at different time points during the experiment