Use of high intensity reflective sheeting in lieu of external lighting of overhead roadway signs
Overhead guide sign lighting has been used by many agencies to improve visibility. However, the availability of newer and more efficient retroreflective materials has created a new challenge for state transportation agencies going through sign sheeting upgrade programs and considering the need for using sign lighting, as there is no existing answer regarding whether upgraded sign sheeting itself can meet drivers’ nighttime visibility demands without external sign lighting. The purpose of the paper is to investigate whether high intensity reflective sheeting can be used to replace overhead guide sign lighting. The conclusion of the study provided a guidance for agencies to adopt their current sign lighting policy. A luminance computation model is used in the paper to calculate overhead guide sign legend luminance under various situations, including different sign lighting technologies, different geometrics and overhead guide sign locations, and different amounts of sign dirt and sign aging. By comparing the calculated luminance of a specific overhead guide sign at a specific situation with the legibility luminance levels required by older drivers, sign lighting needs are assessed. In addition, a life-cycle cost spreadsheet is developed and used to calculate the cost of replacing the current sign sheeting with high reflective sheeting and the cost of installing/upgrading sign lighting. Eventually, the most cost effective approach to maintain overhead guide luminance is discussed.
First published online 16 January 2017
This work is licensed under a Creative Commons Attribution 4.0 International License.
ASTM D4956-09e1:2009. Standard Specification for Retroreflective Sheeting for Traffic Control. http://doi.org/10.1520/D4956-09
Bullough, J. D.; Skinner, N. P.; O’Rourke, C. P. 2010. Legibility of urban highway traffic signs using new retroreflective materials, Transport 25(3): 229–236. http://doi.org/10.3846/transport.2010.28
Carlson, P. J.; Hawkins, H. G. 2003. Minimum Retroreflectivity Levels for Overhead Guide Signs and Street-Name Signs. Report No FHWA-RD-03-082. Federal Highway Administration, McLean, VA, US. 120 p. Available from Internet: https://www.fhwa.dot.gov/publications/research/safety/03082/03082.pdf
FHWA. 2009. Manual on Uniform Traffic Control Devices for Streets and Highways. Federal Highway Administration (FHWA), US Department of Transportation, Washington, DC. 862 p. Available from Internet: http://mutcd.fhwa.dot.gov/pdfs/2009r1r2/pdf_index.htm
Holick, A. J.; Carlson, P. J. 2008. Minimum Retroreflectivity Levels for Blue and Brown Traffic Signs. Report No FHWA-HRT-08-029. Federal Highway Administration, McLean, VA, US. 51 p. Available from Internet: http://www.fhwa.dot.gov/publications/research/safety/08029/08029.pdf
IESNA. 2001. IESNA Recommended Practice for Roadway Sign Lighting. IESNA RP-19-01. Illuminating Engineering Society of North America, New York, NY. 16 p.
INDOT. 2009. Field Evaluation of Unlighted Overhead Guide Signs. Indiana Department of Transportation (INDOT), Indianapolis, Indiana, US.
Jackson, N. M.; Carlson, P. J.; Ye, F.; Jackson, G. R. 2013. Use of High Intensity Reflective Sheeting in-lieu of External Lighting of Overhead Roadway Signs. Report No BDK82 977-07.
Florida Department of Transportation, Tallahassee, FL, US. 82 p. Available from Internet: http://www.fdot.gov/research/completed_proj/summary_mnt/fdot-bdk82-977-07-rpt.pdf
Schoettle, B.; Flannagan, M. J. 2011. A Market-Weighted Description of Low-Beam and High-Beam Headlighting Patterns in the U.S.: 2011. Report No. UMTRI-2011-33. University of Michigan, US. 30 p.
Schoettle, B.; Sivak, M.; Flannagan, M. J.; Kosmatka, W. J. 2004. A Market-Weighted Description of Low-Beam Headlighting Patterns in the U.S.: 2004. Report No. UMTRI-2004-23. University of Michigan, US. 18 p. Available from Internet: https://deepblue.lib.umich.edu/bitstream/handle/2027.42/55198/UMTRI-2004-23.pdf