The State of North Carolina currently maintains approximately 78,000 miles of road and approximately 1 million signs. In the near future, the Federal Highway Administration (FHWA) is expected to release minimum levels for sign retroreflectivity. The pending guidelines will present several new issues to state transportation agencies responsible for sign placement and maintenance, including liability, safety issues, organizational concerns, and resource concerns such as labor and cost. To date, no one has developed a system or methodology to meet the standards on a scale as vast as that faced by NCDOT.
The main objective of this project is to determine, quantify, and present to NCDOT alternative approaches for meeting the standard. The focus of the study is on signs; pavement markings are not being considered. In addition, this report pertains to static signs only. Changeable, temporary, and contracted signs are not considered. Finally, it is not the intention of this project to create a sign inventory, but to evaluate multiple alternatives to assist the state of North Carolina with addressing the forthcoming retroreflectivity guidelines. This project it is not inclusive of municipalities and counties; however, signs on non-state maintained roads are just as much of a concern and the standard is applicable to all signs, not only state maintained signs.
The current sign maintenance and inspection methods of NCDOT were observed and evaluated. A life cycle of a sign in North Carolina was created based on visits to the sign manufacturing plant in Bunn, NC, discussion with NCDOT Signing Engineers, and visits to State Highway Divisions to see storage methods and accompany an actual nighttime sign inspection.
Two studies were performed in conjunction with this report to estimate the number of signs on North Carolina roads because an accurate approximation was unknown. These reports resulted in an estimate of approximately 11,300 signs on Interstate roads, 369,700 signs on primary routes and 605,000 signs on secondary routes.
Research included exploring retroreflectivity and it's principles, sign types and their classifications, sign sheeting types, and software and technologies available for measurement.
Using the existing literature and information collected from NCDOT meetings and observations, a preliminary list of about 30 alternatives was generated. These alternatives were presented to the NCDOT research team to retrieve comments and feedback as to which alternatives they would like to see evaluated. The meeting resulted in four alternatives, which are: Maintain nighttime visual inspection method (current method; Maintain nighttime inspection method with improvements; Implement a sign inventory management system, and Combination of Alternatives 2 and 3. The four alternatives were outlined and costs were generated for each one.
A spreadsheet to determine the accuracy of nighttime sign inspection method was created. It was also used to calculate how many signs would potentially not be in compliance after visual inspection. It was determined that the visual inspection method produces a fairly low percentage of signs that are potentially not in compliance after the inspection. It is anticipated that the percentage of signs potentially not in compliance for NCDOT are lower because of sign personnel experience and that accuracy would increase if improvements were made to inspector training.
