||Traffic signs are an indispensable part of our daily lives. However, the traditional traffic signs with retroreflective sheets and external lighting are|
almost invisible in severe weather such as heavy rains or fogs. With the popularity of LED lighting and display applications, people start to apply LEDs in traffic signs. Due to the characteristics of small light-emitting area and high directivity, LEDs are considered more probable to induce glare that disturbs human’s visual sensation. To investigate the legibility and visual comfort of LED traffic signs, an ergonomic experiment is designed and performed.
Two factors are used in the experiments: the uminance contrast and the luminance of green background. The contrast is defined as the ratio of green-background luminance to white-text luminance. The design criterion for the luminance takes the suggestions from the Bureau of Energy, Ministry of Economic Affairs and IESNA (Illuminating Engineering Society of North America), and is set in the range of 20-500 nit. The contrast is set at 1:2 to 1:11,taken and slightly extended from the comfort region in VDT (visual display terminal) studies. Subjective ratings on legibility and visual comfort are
obtained by questionnaires.
The results show that the luminance contrast is a significant factor for both the legibility and visual comfort, while the green-background luminance is not.
Post hoc comparisons show that the contrast from 1:7 to 1:9 is preferable when considering the legibility and visual comfort at the same time. The contrast less
than 1:5 induces relatively poor visual experiences. Finally, the experimental data are utilized to construct mathematical models of legibility and visual comfort as functions of contrast and green-background luminance. Operating suggestions for LED traffic signs are drawn from the models to provide satisfactory legibility and visual comfort.Keywords: LED traffic signs, Glare, Visual comfort, Legibility
||中華民國經濟部能源局，民國101 年12 月。LED照明節能應用技術手冊，中華民國。|
記者李華庭，民國99 年4 月8 日。嘉市道路加設LED 燈，台灣新聞網。
R. E. Dewar, J. G. Ells, G. Mundy, 1976, “Reaction Time as an Index of Traffic Sign,” Journal: Human Factors and Ergonomics Society, Vol 21, No 2, USA, pp.381-389.
L. Gerald and D. F. Kearns, 1996, “Visibility of Text and Icon Highway Signs under Dynamic Viewing Conditions, ”Human Factors, Vol 38, No4,USA, pp.690-701.
H. J. Schmidt-Clausen and J. T. H. Bindels, 1974, “Assessment of discomfort glare in motor vehicle lighting,” Lighting Research and Technology, Vol 6,
中華民國經濟部能源局，民國102 年8 月9 日。LED 道路交通標誌牌技術規範。
FHWA, 2009, Manual on Uniform Traffic Control Devices, USA.
中華民國交通部國道高速公路局，民國93 年2 月11 日。交通工程標準圖，中華民國。
Illuminating Engineering Society of North America (IESNA), 2001,Roadway Sign Lighting, Recommended Practice RP-19-01, New York.
American National Standard Institute (ANSI), 1988, “American National Standard for Human Factors Engineering of visual display terminal workstations(ANSI/HFS 100-1988 , 1988),” Human Factors and Ergonomics Society, Inc., Santa Monica, California
 J. Wu and Z. Zhu, 1989, “On the standardization of VDT′s proper and optimal contrast range,” Ergonomics, 33(7),China, pp.925-936.
A. Dillon, 1992, “Reading from paper versus screens: a critical review of the empirical literature,” Ergonomics, 35(10), pp. 1297-1326.
M. S. Sanders and E. J. McCormick, 1993, Human Factors in Engineering and Design, No.7, McGraw-Hill, Singapore.
者辨識力及主觀偏好的影響，工業工程學刊，VOL. 18，NO. 2，中華民國，第95-101頁。
P. R. Boyce, 2009. Lighting for Driving: Roads, Vehicles, Signs, and Signals, No.1, CRC, New York.
J. B. De Boer,1967 “Visual perception in road traffic and the field of vision of the motorist,” in Public Lighting, J. B. De Boer ed., Eindhoven, Netherlands, Philips Technical Library, pp.11-96.