In 2020, 844,310 vehicles were involved in crashes while turning left, highlighting the need to research and prevent these collisions. Drivers assess left turns based on time-to-collision (TTC) with an oncoming vehicle and the time required to turn (TRT). However, studies have not assessed whether these turn estimations are accurate. We hypothesized that judgments of the last safe moment to turn would have shorter TTCs for motorcycles due to the size arrival effect. No prior research compares estimated and actual turning times, but walking time studies display accurate estimations, suggesting drivers might also be accurate. We analyzed the minimum TTC when participants indicated the last safe moment to turn left in front of an oncoming vehicle. ANOVA showed that drivers responded sooner (higher TTC) to larger vehicles (trucks) and slower vehicles (30mph) compared to smaller vehicles (motorcycles) and faster (vehicles). The interaction between vehicle size and speed was not significant. For perceived safety margins, drivers had larger margins for trucks and slower vehicles compared to motorcycles and faster vehicles, with no significant interaction. We are continuing to analyze actual turning time data to compare it with imagined turns and assess the accuracy of drivers' judgments and their safety margins.
