@article{immaneni_hummer_rasdorf_harris_yeom_2009, title={Synthesis of sign deterioration rates across the United States}, volume={135}, DOI={10.1061/(ASCE)0733-947X(2009)135:3(94)}, abstractNote={In response to minimum retroreflectivity standards, transportation departments are implementing sign asset management strategies, which rely upon knowledge of how retroreflectivity decreases as signs weather and age. To provide this knowledge, the writers field measured over 1,000 in-service signs in scattered North Carolina Department of Transportation (NCDOT) divisions, collecting age and retroreflectivity data for white, yellow, red, and green signs and for ASTM sheeting Types I and III. Data from this study and data from five similar U.S. efforts were analyzed using regression to identify the best available deterioration rate estimates, finding that retroreflectivity minimums are usually reached eight to 15 years after installation. 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, the writers reevaluated their data i...}, number={3}, journal={Journal of Transportation Engineering}, author={Immaneni, V. P. K. and Hummer, J. E. and Rasdorf, W. J. and Harris, E. A. and Yeom, C.}, year={2009}, pages={94–103} }
 @article{immaneni_rasdorf_hummer_yeom_2007, title={FIELD INVESTIGATION OF HIGHWAY SIGN DAMAGE RATES AND INSPECTOR ACCURACY}, volume={11}, ISSN={["1552-7549"]}, DOI={10.1177/1087724x07299882}, abstractNote={ This study sought to create a simulation model to provide the North Carolina Department of Transportation (NCDOT) with recommendations to improve its sign inspection and replacement procedures. This research focuses on two key factors built into the model: (a) the rate at which signs are damaged beyond usefulness based on natural or man-made causes and (b) the accuracy rate of visual sign inspections based on retroreflectivity. The research team conducted nighttime rides with sign inspectors in 5 of 14 NCDOT divisions. During subsequent daytime rides, the team measured sign retroreflectivity to allow estimation of sign deterioration and inspector accuracy rates. Data were collected for white, yellow, red, and green signs and for sheeting Types I and III. About 2.3% of inspected signs (per year) were damaged to the point of needing replacement, and inspectors did not reject a large percentage of signs that had retroreflectivity values below the proposed minimum Federal Highway Administration standard. }, number={4}, journal={PUBLIC WORKS MANAGEMENT & POLICY}, author={Immaneni, Venkata Pavan K. and Rasdorf, William J. and Hummer, Joseph E. and Yeom, Chunho}, year={2007}, month={Apr}, pages={266–278} }