Citation

Zwahlen HT, Sunkara M, Kellmeyer D, Sundarram S. Transp. Res. Rec. 1994; 1456: 112.

Copyright

(Copyright © 1994, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

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Abstract

RESULTS of five similar but independent field studies investigating the nighttime legibility and conspicuity of two different types of reflective license plates under low-beam illumination are consolidated. In each study reflective sheeting license plates (12 new and 12 used Texas license plates with blue characters on white background) were compared with beads-on-paint reflective license plates [12 new and 12 used Arizona license plates with white characters (beads on paint) on dark red background]. The same set of 48 plates was used in each of the studies. In the legibility studies the license plates were displayed at different distances straight ahead along the longitudinal axis of the experimental car. In the conspicuity studies the plates were displayed either 20 ft (6.1 m) to the right or 20 ft (6.1 m) to the left of the longitudinal axis ahead of the experimental car. A car providing opposing glare was positioned 200 ft (61 m) ahead of the experimental car to simulate a tangent section of a two-lane rural highway at night with an opposing car. The studies were conducted with five independent groups of subjects. Twenty subjects were used to determine the nighttime legibility [75 ft (22.9 m)] and conspicuity [550 ft (167.6 m)] of dry license plates in Study 1, and 12 subjects each were used in the remaining four studies. Studies 2 and 3 investigated the legibility of both dry and wet license plates, respectively, at 50, 75, and 100 ft (15.2, 22.9, and 30.5 m). Study 4 investigated the conspicuity of wet license plates at 550 and 750 ft (167.6 and 228.6 m), and Study 5 investigated the conspicuity of dry license plates at 750 ft (228.6 m). The results of the legibility studies (Studies 1, 2, and 3) indicate that the dry reflective sheeting plates consistently performed slightly better than the dry beads-on-paint plates. Furthermore, the wet reflective sheeting plates provided considerably better legibility performance when compared with that of the wet beads-on-paint plates. The conspicuity results (Studies 1, 4, and 5) indicate a consistent slight to considerable advantage of the dry or wet reflective sheeting license plates over the dry or wet beads-on-paint plates depending on the display location (left or right) at 550 and 750 ft (167.6 and 228.6 m). All these performance differences were statistically significant at the 0.05 level. In general the results of this investigation suggest that the reflective sheeting design is a much more robust product design when compared with the beads-on-paint design, because it will retain a much greater degree of legibility and conspicuity performance under adverse conditions such as opposing car glare or wetness of the plates.

Language: en