Pedestrian-AV interactions at unmarked midblock: Effects of eHMI onset timing and vehicle kinematics on young adult pedestrian behavior and subjective safety perception.

Early eHMI onset significantly reduced pedestrian crossing initiation time compared to late eHMI onset and no eHMI conditions.

• Study used a within-subject repeated measures design with 43 valid young adult pedestrians in a virtual reality (VR) experiment.
• Three eHMI conditions were tested: early eHMI onset, late eHMI onset, and no eHMI.
• Crossing initiation time was one of the key behavioral measures assessed.
• The effect was observed across both early yield and late yield vehicle kinematic conditions.

Early eHMI onset significantly reduced pedestrian entry time into the crossing zone.

• Entry time was measured as part of crossing performance metrics.
• The reduction in entry time indicates faster decision-making and crossing initiation by pedestrians.
• This finding held across the within-subject repeated measures design with 43 participants.
• Both vehicle kinematic conditions (early yield and late yield) were included in the analysis.

Early eHMI onset improved pedestrians' subjective safety perception compared to other eHMI timing conditions.

• Subjective safety perception was assessed as a dependent variable alongside behavioral measures.
• Conditions compared included early eHMI onset, late eHMI onset, and no eHMI.
• The improvement in subjective safety was statistically significant.
• 43 valid young adult pedestrians participated in the VR-based experiment.

The combination of late vehicle yielding and early eHMI onset produced the best crossing behavior and fixation allocation outcomes.

• This interaction condition demonstrated 'optimal crossing efficiency while maintaining safety' per the authors.
• Fixation allocation to the AV was measured as an indicator of pedestrian attention and situational awareness.
• The interaction between vehicle kinematics and eHMI onset timing was a key focus of the study design.
• Two vehicle kinematic conditions were tested: early yield and late yield.

The study examined both vehicle kinematics (implicit communication) and eHMI (explicit communication) and their interaction effects on pedestrian behavior at unmarked midblock crossings.

• Prior research had examined vehicle kinematics or eHMI performance separately, but not their interaction.
• The VR experiment used a within-subject repeated measures design.
• Dependent variables included crossing initiation time, entry time, fixation allocation, and subjective safety perception.
• 43 valid young adult pedestrians were recruited for the study.
• The study setting was an unmarked midblock crossing, identified as a high-risk area for pedestrians.