As autonomous lighting devices, variable message signs (VMS) seem to have some advantages in traffic information releasing in fog weather when compared to static traffic signs. However, it is still not quite clear whether the size of the text height displayed on VMS in normal condition can meet drivers’ cognition requirements under the influences of fog weather. A total of 33 participants were recruited to test the effects of text height on drivers’ visual cognition behaviour by dynamic driving simulation experiments. Four indexes including cognition distance, cognition time, cognition speed and subjective score for VMSs were used to represent driver cognition behaviour. Comparison results between normal and fog weather showed that cognition distance increased significantly as the text height increasing for both two conditions. Under the fog conditions, cognition distance and cognition time were slightly better than that in normal condition. There was no significant difference between cognition speed and driver subjective score between these two weather conditions. Therefore, it was concluded that the height of text displayed on VMS in normal condition was acceptable for driver’s visual requirements in the fog weather.

CICTP