Abstract
According to a 2016 NHTSA report (National Center for Statistics and Analysis, 2016) approximately 50,000 bicyclist injuries and 729 bicyclist fatalities were reported in the United States in the year 2014, with most crashes between motor vehicles and bicycles occuring during daylight hours. Most collisions between motor vehicles and bicyclists involve the bicyclist being struck from behind (Hutchinson & Lindsay, 2009; Kim, Kim, Ulfarsson, & Porrello, 2007). For this reason, it is important that bicyclists be sufficiently conspicuous to drivers who are approaching from behind.
There has been a recent surge in research that applies basic perceptual science to make vulnerable road users more easily noticed by drivers. For example, humans’ perceptual sensitivity to biological motion (or “biomotion”; Johansson, 1973) can be used to enhance the conspicuity of pedestrians at night (for a review, see Tyrrell, Wood, Owens, Whetsel-Borzendowski, & Stafford-Sewall, 2016). Similar findings, using either retroreflective tape or LEDs, have been found to apply to cyclists’ conspicuity as well (e.g., Kwan & Mapstone, 2004; Wood, et al., 2012; Costa, et al., 2017). Taken together, the existing evidence makes it clear that efforts to enhance the conspicuity of both pedestrians and bicyclists – possibly including fluorescent apparel in daylight – are most effective when capitalizing on drivers’ perceptual sensitivity to biomotion. As such, this project explored the potential value of using fluorescent apparel strategically to make bicyclists more conspicuous to drivers during daylight hours. Specifically, we examined the influence of four different clothing configurations on the distances at which participants recognize the bicyclist wearing them.
Methods. Visually healthy observers (N=186; mean age = 18.7 years) searched for bicyclists while a researcher drove them along a pre-determined route on public roads. Experimenters instructed participants to press a button on a numeric keypad each time they were confident that they recognized any person “on or with” a bicycle, who was “stopped or moving,” and who was “in or near the roadway.” Approximately seven minutes into their trip, participants encountered an experimenter wearing one of four outfits, pedaling (75 - 90 rpm) on a stationary bicycle on a sidewalk to the right of the roadway while facing away from the approaching vehicle. Experimenters delivered instructions to participants in such a way that was designed to limit participants’ expectancy that they would encounter a planted/scripted researcher on a bicycle during their trip.
Participants’ button presses initiated a timer on the laptop computer operated by an experimenter in the back-seat of the research vehicle. The back-seat experimenter then stopped the timer once the test vehicle passed the test bicyclist. The elapsed time was used to calculate each participant’s response distance (distance = speed × time). This technique has been used in numerous on-road pedestrian conspicuity experiments, and its accuracy has been verified for stationary roadway stimuli (e.g., Fekety, Edewaard, Stafford-Sewall, & Tyrrell, 2016; Whetsel-Borzendowski, Stafford-Sewall, Rosopa, & Tyrrell, 2015).
After passing the experimenter bicyclist, the participants were informed that data collection had ended. Participants were then interviewed and debriefed while being driven back to the starting location. Each experimental session lasted approximately 30 minutes.
Results. We performed a one-way between-subjects analysis of covariance (ANCOVA) to test the significance of the effects of clothing configuration on the response distances. The main effect of clothing was statistically significant, F(3,120) = 16.072, η2 = .287, p < .001. Thus, the participants’ response distances significantly varied among the four clothing configurations. Post-hoc pairwise comparisons (Bonferroni) revealed that that a fluorescent yellow jersey did not significantly improve the cyclist’s conspicuity relative to a black jersey. However when the cyclist paired the fluorescent jersey with fluorescent yellow leggings, participants responded from a distance 3.3x farther than an identical outfit with black leggings.
Discussion. The finding that fluorescent yellow leggings can provide a dramatic enhancement to bicyclist conspicuity is, we believe, a consequence of highlighting the bicyclist’s pedaling motion. The rhythmic up-down movements of a cyclist’s lower legs uniquely specify a pedaling motion that is visually distinct from, for example, a pedestrian walking or jogging. Further, considerable research has identified that highlighting a cyclist’s biological motion can provide powerful conspicuity enhancements. Thus fluorescent leggings can offer a powerful and low-tech tool for enhancing bicyclists’ daytime conspicuity.
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