Study On The Legibility Of Chinese Character On LED Road Traffic Sign When Driving At Nighttime

At present,the number of urban roads in China is increasing to promote the growth of the national economy.At the same time,the traditional road traffic signs have been replaced by the VMS?Variable Message Sign?,which is gradually dominated by LED display technology,with the continuous innovation of technology.However,in practical applications,VMS lacks the perfect theoretical guidance and urban management system,so it does not achieve its proper utilization rate;and the relevant specifications of VMS in each country have different standards for the brightness and other visual parameters.In this paper,the LED variable road traffic sign information display?VMS?is taken as the research object,and the research is based on the brightness of the Chinese character information at night and its visual impact under the influence of the background brightness environment.The visual recognition method is used to carry out the relevant visual recognition experiment.The method comprehensively considers the influence of each visual recognition factor and discusses the visual recognition effect under the influence of brightness and brightness contrast;Based on the existing papers of VMS,the article sorts out the regulations of different countries in the guidelines and norms,analyzes the research theory and research methods based on road traffic signs,and clarifies the basis of the research on visual recognition theory.In the second chapter of the thesis,we first introduce the visual work characteristics of drivers in night driving,and establish and set visual efficacy experiment through the induction of the relevant theoretical basis of visual effects,combined with the characteristics of this research object and research objectives.The third chapter introduces the theoretical basis of VMS application and analyzes its functional characteristics.This chapter chooses dot matrix VMS as the research object.In view of the many problems existing in the current VMS application in the field investigation,this chapter describes the on-site measurement of the brightness,size,viewing distance and other factors of VMS,and verifies the visual identity of VMS Chinese characters through subjective questionnaires.After the interpretation and investigation of the normative provisions,the thesis combines the theoretical basis and actual status of the previous chapters to set the experimental situation and related parameters.Finally,combined with visual power research theory and experimental psychology method to carry out related visual experiments in controlling other related variables,and finally determined red,green and yellow respectively through two-step experiments of"sharpness discrimination"and"subjective comfort evaluation".The optimal brightness threshold interval and the visual relationship curve under the influence of brightness of the three display fonts at different background brightness at night;the results verify the irrationality of the nighttime brightness value in the current specification,and solve the specific brightness control problem.Provide a basis for the study of visual identity theory in the intermediate visual state.Through the visual efficacy experiment,the overall analysis of the test data,in this part,includes the following three aspects:?1?The reasonable brightness range of the yellow,green and red colors of the road segments under different lighting conditions was obtained.The reasonable brightness intervals of the three display colors showed an increasing trend with the increase of the background brightness.?2?The visual clarity of yellow and red is strongly correlated with visual comfort,while the green is less relevant.?3?The corresponding relationship between the visual target brightnessand the visual correctness rate and the function fitting curve and the brightness contrast C_L visible correct rate are obtained,and the function fitting curve is obtained.1)The variance of the green R² in the two fitting curves is greater than that of yellow and red,which means that the overall visual recognition accuracy curve of green is more in line with the functional relationship trend;2)The peaks of the visual recognition accuracy of the three colors under different environmental background brightness conditions provided by the experiment have strong same regularity,and the visual texture under the intermediate visual state is analyzed.The paper achieved the following innovations:?1?It is proposed that the 4.9 logarithmic corrected visual acuity index of Chinese driver is used as the visual reference standard,and the visual distance corresponding to different visual acuity is determined by the proportional scaling relationship between the viewing angle and the distance,and on the basis of this,different visual acuity dimensions are established.The experiment visually recognizes the distance calculation model.?2?The size conversion factor K between the Landolt-C ring and the Chinese character under the positive contrast condition is determined..?3?The most reasonable brightness range corresponding to red,green and yellow light colors in different nighttime background brightness environments is determined.