Differences in Driver Visual Fixations of Left-Turning Vehicles Between Signalized and All-Way Stop Intersections

Author(s): Caren, Ziraldo, Oliver

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Many car crashes occur at intersections with the most frequently occurring crashes involving at least one vehicle making a left-hand turn. Inadequately searching surroundings and falsely assuming another driver’s next actions commonly result in intersection collisions.


To determine if there are differences in driver visual fixations of left-turning vehicles between signalized and all-way stop intersections where the through driver must decide whether to proceed through the intersection.


22 licensed drivers (N=22; 26.6±10.3 years; 13 women) participated in a driving simulation study in an OKTAL full car driving simulator while wearing Tobii Pro Glasses 3 eye-tracking glasses. After a ten-minute familiarization drive, participants encountered two hazardous scenarios in a counterbalanced order the first of which was a vehicle stopped in the left-hand turn lane of a signalized intersection (SIH) which turned left as the light turned yellow with the participant driver in the dilemma zone. The other hazard was a vehicle approaching an all-way stop (ASH) at the same time as the participant driver, stopping before crossing the intersection. Eye-tracking measures included time to first fixation (TTFF), total fixation duration (TFD), and number of fixations (NF) before and after hazard onset. Before onset was the time from the first reasonable visibility of the hazard vehicle until the vehicle's first movement into the intersection. After onset was the time from onset until the hazard was no longer visible.


Before and after onset, ANOVA (p0.05) revealed that the TTFF was faster for the ASH than the SIH (Before: p=0.005, After: p=0.011). The TFD was longer for the ASH than the SIH (Before: p=0.001), After: p=0.014). NF was also greater for the ASH than the SIH (Before: p<0.001, After: p=0.014).


Movement in the ASH was probably more salient to the participant driver causing them to attend sooner to the hazard, resulting in a faster TTFF, holding their attention as the driver kept looking at the vehicle resulting in the longer TFD and increased NF. After onset, the ASH was looked at earlier and longer as the participant had already come to a stop at the stop sign and now just needed to decide who had priority to proceed. Drivers slowed when approaching the stop sign potentially allowing more time to view other vehicles. In the SIH, driver mental load probably increased, in part from having to decide whether to go through the yellow light. Since the decision to go through the stop sign-controlled intersection was dependent on who got to the intersection first, the driver may have continually monitored the hazard vehicle to determine when the hazard vehicle would arrive. In contrast, the SIH vehicle had been waiting to turn left before the participant driver reached the intersection, therefore, the participant driver may have expected it to remain stopped therefore not requiring further observation.


Although both scenarios required a decision, the decision required for the signalized intersection was more complex. This increased complexity resulted in drivers fixating the potential hazard later and less than a similar hazard in a less complex intersection scenario.