Assessment of Background Complexity of Overhead Guide Signs Image Processing of Digital Images of Nighttime Roadway Scenes

Transportation Research Record: Journal of the Transportation Research Board, No. 2384, Transportation Research Board of the National Academies, Washington, D.C., 2013, pp. 74–84. DOI: 10.3141/2384-09 H. Ge and Y. Zhang, Zachry Department of Civil Engineering, Texas A&M University, 3136 TAMU, College Station, TX 77843-3136. J. D. Miles and P. J. Carlson, Texas A&M Transportation Institute, Texas A&M University System, 3135 TAMU, College Station, TX 77843-3135. Corresponding author: H. Ge, [email protected]. sign. Figure 1 contains images of test signs in settings of varying background complexity. The complexity of the background of an overhead guide or street name sign can make detecting and obtaining information from the sign difficult, particularly in urban conditions, where the background can be very complex. Although the Manual on Uniform Traffic Control Devices does discuss sign visibility, it does not expressly mention or discuss the consideration of background complexity and its potential impact (1). The concept of and concern for background complexity has been developing over the years as state practitioners adapt to expanding urban environments. Although various studies have been indirectly related to the concept of background complexity, NCHRP Project 5-20, Guidelines for Nighttime Visibility of Overhead Guide Signs, was initiated specifically to address growing practitioner concern about whether overhead guide signs need lighting, especially in complex urban environments. A new method or system independent of human perception is needed to assess the background complexity of traffic signs in nighttime environments with high accuracy and consistency. This study aimed to design a system that automatically evaluates the background complexity of overhead traffic signs by using digital images of nighttime roadway scenes, image-processing techniques, and multiple linear regression (MLR). The proposed system has the potential to be combined with the current system for measuring the visibility of traffic signs in practice.