Glancing Behavior of Riders vs. Drivers at Unsignalized Right Turns

Introduction

Motorcyclists are the road user group with the highest likelihood of a fatality; in 2014, the fatality rate per rider was six times greater than that of all drivers, and the number of deaths per mile traveled was over 27 times the number in cars. A large proportion of fatal crashes involving riders occur within intersections or when turning, often due to a failure to yield.,, The increased vulnerability of riders is attributed to factors such as the lack of protection from an enclosed vehicle, decreased stability, and reduced visibility compared to other vehicles. Previous studies have suggested that motorcycle riding experience might lead to safer driving behaviors and increased hazard perception performance that could transfer to car driving.

The purpose of this on-road study was to investigate the differences in anticipatory scanning behaviors of riders and drivers when making right turns at unsignalized intersections., Right-turn scenarios are important because they require a longer acceleration time in the lane and necessitate glances to both the right and left, offering further insight into intersection habits. This research examined anticipatory glances—defined as glances toward the area of the next greatest conflict after crossing the stop line or yield line—to understand potential scanning differences between cohorts.,

The study tested two primary hypotheses:

1. Hypothesis 1: Driver-riders make more secondary glances while riding a motorcycle compared to when they drive a car.
2. Hypothesis 2: Driver-riders make more secondary glances than drivers-only when driving.

Methodology

The study employed an on-road experiment to compare the scanning behaviors of two distinct groups as they navigated right turns at two specific unsignalized intersections in Massachusetts.,

Participant Characteristics: The study included 30 participants.

1. Driver-Rider Group (20 participants): Individuals licensed to drive a car and holding a motorcycle endorsement (mean age = 42.9 years).,
2. Driver-Only Group (10 participants): Individuals who held only a driver’s license and were not motorcyclists (mean age = 34.3 years).,

Data Collection Procedures: Participants wore ASL MobileEye eye tracking glasses under a special helmet or visor, which integrated eye movement data with the forward (world) view, represented by an overlaid crosshair. The eye tracking video allowed a blind scorer to record glances towards the left, right, or ahead using frame-by-frame analysis. Each driver-rider used their own motorcycle, while the car used for the experiment was a 2008 Honda Accord. The route included two unsignalized right turns: one onto a divided street (Massachusetts Avenue) and one onto a street past a rotary (Governors Drive).,, The driver-rider cohort completed the route once while riding and a second time while driving, with the order counterbalanced.,

Analytical Methods: The dependent variable was anticipatory glance behavior, analyzed separately for glances toward the left, right, and across the intersection., Glance count data were aggregated into two time bins: pre-intersection ($\le$ 3 seconds before the stop/yield line) and post-intersection (0 to $\le$ 3 seconds after the stop/yield line)., Data were analyzed using a 2x2x2 mixed-factor Bayesian analysis, with Bayes factors ($B_{10}$) used to measure the evidence favoring the effect of interest. Bayes factors below 3 were considered “anecdotal” evidence, while those greater than 3 indicated strong evidence for the presence of the effect.

Results

The study’s results supported Hypothesis 1, finding that anticipatory glances differed significantly depending on whether the driver-rider was riding or driving, but did not support Hypothesis 2 regarding skill transfer.

Glancing Behavior Within the Driver-Rider Group (Riding vs. Driving):

• Glances to the Left: Participants made decisively more glances to the left when riding a motorcycle than when driving a car. When turning right, the major threats come from the left, and this increased attention suggests that riders pay more attention due to their vulnerability. Furthermore, the time-based difference (more glances before than after the entry) was greater when driving a car than when riding a motorcycle.
• Glances to the Right: Riders made substantially more glances to the right after the entry than before the entry, and this difference was more pronounced in the Intersection scenario compared to the Roundabout scenario.

Glancing Behavior Between Cohorts (Driver-Riders Driving vs. Drivers-Only):

• Lack of Transfer: The data did not show a substantial difference in glancing behavior (left, right, or across) between the driver-rider cohort and the driver-only cohort when they were both driving. This finding means Hypothesis 2 was not supported and suggests that the hazard anticipation skill from riding may not transfer to driving a car.

Influence of Intersection Type: Post-hoc analysis showed that in the Roundabout scenario, participants in both groups made substantially more glances to both the left and the right before entering the intersection than immediately after the entry.,

In summary, the key finding is the illustration of the difference in anticipatory glance behaviors when driver-riders were riding versus driving, suggesting potential for targeted training programs.

References

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