Variable-message signs, which are an important type of traffic sign, have been widely used in traffic control. This study examines the influence of text luminance, text colour and background luminance of variable-message signs on legibility in urban areas under night-time vision. First, the background luminance of variable-message signs in typical urban areas is investigated, tested and classified as high, medium or low depending on the obtained values (3.0, 1.0 or 0.1 cd/m2, respectively). Second, a calculation model is established for the experimental visual recognition distance under different visual acuity conditions, the experimental luminance interval is determined based on psychophysical magnitude perceived, and a legibility experiment is performed using Landolt-C rings. Finally, the reasonable luminance interval (minimum [replacement] luminance), optimal luminance and changing trends of luminance for red, green and yellow colours under different background luminances are obtained such that the legibility requirement is satisfied. The results indicated that different colours have different luminance interval and optimal luminance under different background luminances. This study is of great importance in determining the reasonable luminance of variable-message sign texts and improving the safety and efficiency of road traffic. In the future, these research results are expected to serve as guidelines for variable-message sign setup and management.
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References
1.
ShaunBSigalKCarloG. Road signage comprehension and overload: the role of driving style and need for closure. Transportation Research Procedia2017; 24: 42–449.
2.
DahlstedtS. Luminance uniformity and legibility of traffic signs. Lighting Research and Technology1974; 6: 217–221.
3.
RobertoD. The visibility, colour and measuring requirements of road signs. Lighting Research and Technology1980; 12: 206–212.
4.
SchnellTYekhshatyanLDaikerR. Effect of luminance and text size on information acquisition time from traffic signs. Transportation Research Record2009; 2122: 52–62.
5.
SchnellTAktanFLiC. Traffic sign luminance requirements of nighttime drivers for symbolic signs. Transportation Research Record2004; 1862: 24–35.
6.
Carlson PJ, Hawkins HG. Updated minimum retroreflectivity levels for traffic signs. Federal Highway Administration Report FHWA-RD-03-081. Washington, DC: U.S. Department of Transportation, 2003, p. 107.
7.
Schnell T. Legibility optimization of uppercase text for displaying messages in traffic applications. Ph.D. Dissertation, Ohio University, Athens, 1998.
8.
Aktan F, Schnell T. Defining threshold and confident legibility contrast and luminance needs of nighttime drivers for achromatic and chromatic signs. In: 17th Biennial symposium on visibility and traffic control devices of the transportation research board, Washington, DC, USA, 4–6 April, 2005.
9.
BlackwellOMBlackwellHR. Visual performance data for 156 normal observers of various ages. Journal of Illuminating Engineering Society1971; 1: 3–13.
10.
Zwahlen HT, Xiong S. Legibility of text on traffic signs as a function of luminance and size. In: 80th Annual meeting of the transportation research board, Washington, DC, USA, 7–11 January, 2001.
11.
SivakMOlsonPL. Optimal and minimal luminance characteristics for retroreflective highway signs. Transportation Research Record1985; 1027: 53–57.
12.
Russell ER, Rys M, Rys A, Keck M. Characteristics and needs for overhead guide sign illumination from vehicular headlamps. Federal Highway Administration Report FHWA-RD-98-135. Mclean, VA, USA: U.S. Department of Transportation, 1999.
13.
Jenkins SE, Gennaoui FR. Terminal values of road traffic signs. Australian Road Research Board Ltd. Special Report 49. Vermont South, Victoria, Australia: Australian Road Research Board Ltd., 1986.
14.
LasauskaiteRReisingerM. Optimal luminance of internally illuminated wayfinding signs. Lighting Research and Technology2017; 49: 521–533.
15.
Freyssinier J, Narendran N, Bullough J. Luminance requirements for lighted signage, Proc. SPIE 6337, 63371 M, 12 September 2006.
16.
European Committee for Standardization. Road vertical signs—variable message traffic signs. Irish Standard I.S. EN 12966:2014. Brussels, Belgium, 2014.
17.
United States Sign Council. Sign legibility, overview and calculation methodology, sign legibility index. Member Resource Folio/Legislative Information. Bristol, PA: United States Sign Council, 1998: 2 p.
18.
Federal Highway Administration. Manual on uniform traffic control devices. New Jersey: U.S. Department of Transportation, 2009.
19.
Schieber F, Burns DM, Myers J, Willan N, Gilland J. Driver eye fixation and reading patterns while using highway signs under dynamic nighttime driving conditions: effects of age, sign luminance, and environmental demand. In: 83rd Annual meeting of the transportation research board, Washington, DC, USA, 11–15 January, 2004.
20.
Chrysler ST, Carlson PJ, Hawkins HG. Nighttime legibility of ground mounted traffic signs as a function of font, color, and retroreflective sheeting type. Texas Department of Transportation Report FHWA/TX-03/1796-2. Austin, Texas, USA: Texas Department of Transportation, 2002.
21.
Mace DJ. Transportation in an aging society: improving mobility and safety for older persons. Transportation Research Board Special Report 218. Washington, DC: 1988, pp. 270–293.
22.
JiangHHanWZhangZ. Study of relationship between word height and recognition for traffic guide signs. Journal of Highway and Transportation Research and Development2009; 26: 115–120.
23.
Chen YC, Huang TY, Lee TX, Sun CC. Visual ergonomic evaluations on four different designs of LED traffic signs. In: Current developments in lens design and optical engineering XVIII, proceedings of SPIE optical engineering + applications, San Diego, California, United States, 6–10 August, 2017; Volume 10375.
24.
PadmosPvan den BrinkTDJAlferdinckJWAMFollesE. Matrix signs for motorways: system design and optimum photometric features. Lighting Research and Technology1988; 20: 55–60.
25.
BoycePR. Lighting for driving: roads, vehicles, signs, and signals, Boca Raton, Florida, USA: CRC Press, 2009, pp. 79–124.
26.
Burley, M. Guidelines for variable message signs. East Perth, Australia: Main Roads Western Australia, 2015, https://www.mainroads.wa.gov.au/Documents/Guidelines for VMS_Final.RCN-D15%5E23557581.PDF (accessed 18 February 2020).
GA 484-2010, LED variable message sign of road traffic inducement. Beijing, China: Standards Press of China, 2011.
29.
GB/T31446-2015, LED active light-emitting road traffic signs. Beijing, China: Standards Press of China, 2009.
30.
RocaJInsaBTejeroP. Legibility of text and pictograms in variable message signs: can single-word messages outperform pictograms?. Human Factors2018; 60: 384–396.
31.
HouDHuangKHanW. Study on Chinese character height model for traffic guide signs based on perceive characteristics of Chinese drivers. Journal of Highway and Transportation Research and Development2010; 27: 142–146.
32.
WinterJFotiosSVolkerS. The effect of assuming static or dynamic gaze behaviour on the estimated background luminance of drivers. Lighting Research and Technology2019; 51: 384–401.
33.
CIE Central Bureau. Guide for the lighting of road tunnels and underpasses. CIE 88: 2004. Vienna, Austria, 2004.
34.
CIE Central Bureau. Guide for the lighting of road tunnels and underpasses. CIE 88: 1990. Vienna, Austria, 1990.
35.
StevensJCStevensSS. Brightness function: effects of adaptation. Journal of the Optical Society of America1963; 53: 375–385.
36.
BodmannHWToisonML. Predicted brightness-luminance phenomena. Lighting Research and Technology1994; 26: 135–143.
37.
StevensSS. The surprising simplicity of sensory metrics. American Psychologist1962; 17: 29–39.
38.
GB 5768.2-2009, Road traffic signs and marking part 2: road traffic signs. Beijing, China: Standards Press of China, 2009.
39.
Qiu Z. Study on the legibility of Chinese character on LED road traffic sign when driving at nighttime. Master’s thesis, Chongqing University, P.R China, 2019.
40.
ZhangB. The identification of Chinese characters in traffic signs. Journal of Highway and Transportation Research and Development1993; 10: 40–46.
41.
ReaMSOuelletteMJ. Relative visual performance: a basis for application. Lighting Research and Technology1991; 23: 135–144.
