Citation

Zwahlen HT, Jin YP. Transp. Res. Rec. 1995; 1495: 99-106.

Copyright

(Copyright © 1995, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Monocular and binocular curve radius perception accuracy of ten young drivers under curve approach and nighttime conditions using a 1:50 scaled laboratory setup was investigated. The experiment consisted of a sequential comparison of a 90 deg segment of a right curve with a standard radius equipped with 12 equally spaced 1:50 scaled retroreflective yellow/black miniature chevron signs with a 90 deg segment of a test curve (right curve), which could have either 2, 3, 4, or 8 equally spaced 1:50 scaled retroreflective miniature chevron signs along a curve radius of either 95, 97.5, 100, 102.5, or 105% of the standard curve radius. For each experimental presentation the standard curve was presented first to the subjects (black road environment and chevrons illuminated by electrically controlled headlamps) for 2 sec, then the subjects rotated 90 deg and were presented with the test curve (1 of 5 curve radii, with either 2, 3, 4, or 8 equally spaced chevrons) for 2 sec. A forced-choice response (smaller, larger than standard curve radius) was required from the subjects. All experimental conditions (5 radii, 4 chevron levels, 5 replications for each subject) were randomized within a viewing condition for each subject. The curve approach viewing distance from the subject's eyes to the beginning of the 90 deg segment of the curve was 4.57 m, which represents 228.6 m in the real world, whereas the curve radius of the standard curve was 0.914 m, which represents a curve radius of 45.6 m (38 deg curvature) in the real world. All chevrons were within a total visual field of view of about 11 deg. The overall averages for the percentage of the number of correct responses were calculated for the 2-, 3-, 4-, and 8-chevron conditions for each radius of the test curve for binocular viewing and monocular viewing, and these percentages were plotted against the number of chevrons. The average of correct responses for the 5 test curve radii increases for the binocular viewing conditions from 56% for 2 chevrons, to 62.5% for 3 chevrons, to 82.5% for 4 chevrons, and remains about the same (81.0%) for 8 chevrons. For monocular viewing, the average correct responses increase from 50% for 2 chevrons, to 64% for 3 chevrons, to 70.5% for 4 chevrons, and remains about the same (72.5%) for 8 chevrons. Overall, for the 5 test curve radii and for the 4 chevron levels, the binocular viewing condition (especially for 4 and 8 chevrons) produces on the average a somewhat higher overall average value for correct responses (70.6% vs 64.3% monocular). On the basis of analysis of variance, the curve radii, the number of chevrons, and the viewing conditions are all statistically highly significant factors (0.05 level, interactions not significant). Considering the monocular results as more applicable for the real-world curve approach, it is concluded that, for the conditions investigated in this study, 4 equally spaced chevrons within a total visual field of about 11 deg provide adequate curve radius estimation cues for drivers approaching an unfamiliar curve at night.

Record URL:
http://onlinepubs.trb.org/Onlinepubs/trr/1995/1495/1495-012.pdf

Language: en

Keywords

Automobile drivers; Traffic signs; Visibility; Statistical methods; Binocular vision