Biomedical subjects

Richard A Tyrrell

Publications and source records attributed to Richard A Tyrrell.

5 recordsLinked to original sources

PubMed2005

The effects of severe visual challenges on steering performance in visually healthy young drivers.

PURPOSE: Two experiments explored the extent to which induced blur, reduced luminance, and reduced visual fields affect drivers' steering performance in a driving simulator. METHODS: In experiment 1, ten young participants (M = 21.2 years) drove at approximately 89 km/h (55 mph) along a curvy roadway while being exposed to blur (0 to + 10 D), luminance (0.003 to 16.7 cd/m), and visual field (1.7 and 150 degrees) manipulations. In experiment 2, a new group of ten young participants (M = 18.5 years) drove while exposed to seven visual field sizes (1.7 to 150 degrees). RESULTS: Steering was sensitive to a reduced field size but not to the blur and luminance challenges. Acuity, on the other hand, was sensitive to the blur and luminance challenges but not to reduced field size. DISCUSSION: In healthy young drivers, steering performance is remarkably robust to severe blur and to extremely low luminances. These results support a key element of the selective degradation hypothesis advanced by Leibowitz and colleagues--that steering abilities are preserved at night even when the ability to recognize objects and hazards is not. Additional research should address the other element of this hypothesis--that drivers fail to appreciate the extent to which their visual abilities are degraded at night.

Adult↗

PubMed2005

Limitations in drivers' ability to recognize pedestrians at night.

This study quantified drivers' ability to recognize pedestrians at night. Ten young and 10 older participants drove around a closed road circuit and responded when they first recognized a pedestrian. Four pedestrian clothing and two beam conditions were tested. Results demonstrate that driver age, clothing configuration, headlamp beam, and glare all significantly affect performance. Drivers recognized only 5% of pedestrians in the most challenging condition (low beams, black clothing, glare), whereas drivers recognized 100% of the pedestrians who wore retroreflective clothing configured to depict biological motion (no glare). In the absence of glare, mean recognition distances varied from 0.0 m (older drivers, low beam, black clothing) to 220 m (722 feet; younger drivers, high beam, retroreflective biomotion). These data provide new motivation to minimize interactions between vehicular and pedestrian traffic at night and suggest garment designs to maximize pedestrian conspicuity when these interactions are unavoidable.

Adult↗

PubMed2004

On-road measures of pedestrians' estimates of their own nighttime conspicuity.

PROBLEM: Most pedestrian fatalities occur at night. Although researchers have long understood that drivers have difficulty seeing pedestrians at night and that reflective clothing can dramatically enhance pedestrian conspicuity, the extent to which pedestrians understand these facts is unclear. This experiment quantified pedestrians' estimates of the ability of an approaching driver to recognize the presence of roadside pedestrians. METHOD: Ten younger and 10 older participants walked in place on the far shoulder of a closed-road circuit and pressed a button when they were confident that the approaching driver could first recognize that a pedestrian was present. RESULTS: Pedestrians overestimated their visibility and dramatically underestimated the benefit of conspicuity treatments. CONCLUSIONS: These results suggest that pedestrians fail to understand the magnitude of the nighttime conspicuity problem and the value of conspicuity treatments. Pedestrians may therefore unknowingly place themselves in danger at night. IMPACT: These results underscore the need to educate pedestrians about the dangers of interacting with traffic at night and about treatments that increase their safety.

Accidents, Traffic↗

PubMed2004

Educational interventions successfully reduce pedestrians' overestimates of their own nighttime visibility.

Pedestrians dramatically overestimate their own visibility at night. This is likely to result in pedestrians unknowingly engaging in dangerous behavior. To determine the extent to which pedestrians' estimates of their own visibility are influenced by educational interventions, clothing reflectance, and headlamp beam setting, participants in 2 experiments estimated their own nighttime visibility by walking toward a stationary car to the point where they believed they were just recognizable as a pedestrian. In the first experiment 48 university students were tested and in the second experiment 9 high-school driver education students were tested. Overall, participants failed to appreciate the benefits of reflective clothing and of high-beam illumination. However, the participants in Experiment 1 who had heard a relevant lecture several weeks earlier gave estimates that were 10% shorter than did a control group. Participants in Experiment 2 heard a more focused and graphic-intensive lecture and gave estimates that were 56% shorter than did a control group. Potential applications of this research include increasing pedestrian safety by designing and implementing research-based public education campaigns aimed at reducing pedestrians' overestimates of their own nighttime visibility.

Accidents, Traffic↗

PubMed2003

Accommodation and vergence require effort-to-see.

PURPOSE: Accommodation and vergence both appear to be influenced by multiple nonsensory factors. "Effort-to-see" is one of these factors. This study was designed to assess the extent to which effort-to-see affects accommodation and vergence. METHOD: Nine volunteers participated in this study. Stimuli were chosen to stimulate selectively either accommodation or vergence. Accommodation and vergence responses were measured while observers viewed each stimulus with the instruction of "concentrate" or "space-out." RESULTS: Both oculomotor adjustments were accurate when observers "concentrated," but regressed toward the resting posture during identical stimulus conditions when observers spaced-out. Interesting, individual differences in oculomotor behavior were apparent. CONCLUSION: This study demonstrates that higher-level attentional factors play an important role in accommodation and vergence for active exploration of the three-dimensional environment.

Accommodation, Ocular↗