Fixation distance and fixation duration to vertical road signs

Area of Science:

• Human-Computer Interaction
• Traffic Safety Research
• Cognitive Psychology

Background:

• Understanding driver visual behavior is crucial for road safety.
• Previous research has explored visual attention to road infrastructure, but specific fixation distances to vertical road signs require further investigation.

Purpose of the Study:

• To determine the distance at which drivers first fixate on vertical road signs.
• To analyze the relationship between fixation distance, driving speed, and fixation duration.
• To establish the minimum presentation time required for accurate road sign identification.

Main Methods:

• A driving study involving 22 participants on an 8.34 km route with 75 road signs.
• Eye-movement tracking synchronized with GPS and kinematic data to record first-fixation distances and durations.
• A staircase procedure to determine the visual presentation time threshold for 75% accurate road sign identification.

Main Results:

• The median first-fixation distance to road signs was 51 meters (m).
• Median fixation duration was 137 milliseconds (ms), with a modal value of 66 ms.
• First-fixation distance showed a linear relationship with driving speed and fixation duration; signs were fixated significantly closer than their visibility distance.
• The presentation-time threshold for 75% accurate identification was 35 ms.

Conclusions:

• Drivers attend to road signs at distances considerably closer than their maximum visibility range.
• Short fixation durations, as low as 35 ms, are sufficient for drivers to correctly identify road signs.
• Findings have implications for road sign design, placement, and driver attention management strategies.