Sign Maintenance Strategies for Agencies to Comply with the FHWA Minimum Retroreflectivity Standards

A new highway sign management and minimum retroreflectivity standard issued by the Federal Highway Administration (FHWA) is compelling highway agencies to re-evaluate how they manage their signs and determine how to comply with the standard while remaining within their budgets. To demonstrate compliance with these standards, agencies will need to have a traffic sign management method in place. This research created models for sign deterioration and sign management that agencies can use to determine how to modify their traffic sign management practices to maintain a high level of safety on the road in a cost-effective manner.;Sign management methods rely upon knowledge of how retroreflectivity decreases as signs weather and age. To provide this knowledge, data collected for a North Carolina Department of Transportation (NCDOT) sign study and data from five similar US efforts were analyzed using regression to identify the best available deterioration models. Initial results indicated that the best-fitting relationships between retroreflectivity and age were generally linear and that these models were significant despite having low R2 values. Because age did not explain some of the variance, a re-evaluation of the data including NCDOT divisions as a factor found that sign deterioration differed significantly by division.;Currently, there is limited information about the long-term deterioration of ASTM Type III and IX signs. One way of achieving a better understanding of long-term sign deterioration is to establish an experimental sign retroreflectivity measurement facility (ESRMF). An ESRMF is an arrangement of signs in a controlled area that have their retroreflectivity measured at regular intervals to determine how it deteriorates as a function of time. This thesis describes how such a facility should look and why. A template is presented that can be used by agencies nationwide for collecting critical sign data to inform policy decisions.;Next, a unique microscopic sign system simulation was developed to quantitatively evaluate the effectiveness of various sign management practices for a wide variety of agencies. Using the Arena simulation software, the author built and validated a simulation model where each sign was represented as a separate entity and moved through a network of sub-models replicating the management and environmental processes experienced annually. The simulation includes sub-models for sign damage, inspection, replacement, and deterioration that are modifiable by key input parameters. The simulation model produces several key estimates on an annual basis for the purpose of comparing different sign management scenarios. The analysis focused on three management methods - nighttime visual inspection, blanket replacement, and expected sign life - and two key sign maintenance functions, sign damage and replacement.;The scenarios comparative analysis found that sign damage is a contributor to sign condition and that sign managers should make prompt replacement of damaged signs a priority. The blanket replacement method was found to be less cost-effective than the nighttime visual inspection method. The expected sign life method was competitive on costs with the visual inspection method. Training inspectors to be more accurate when judging retroreflectivity can realize further savings. Skipping inspection or replacement one year, or having an insufficient sign budget, can lead to degraded sign condition levels. Based on these findings, the author offers five best practices that agencies can consider when making sign management decisions.