Field Investigation of Highway Sign Damage Rates and Inspector Accuracy

Abstract

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.

Keywords

sign retroreflectivity inspect damage vandalism inspector performance

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References

American Association of State Highway and Transportation Officials. (2000). Minimum levels of retroreflectivity for signs. Retroreflectivity policy resolution. Appendix E—AASHTO Policy Resolution. Washington, DC: Author .

Black, K.L. , McGee, H.W. , Hussain, S.F. , & Rennilson, J.J. (1991). Service life of retroreflective signs (FHWA-RD-90-101). Washington, DC: Federal Highway Administration.

Carlson, P.J. , & Hawkins, H.J. (2003). Updated minimum retroreflectivity levels for traffic signs (FHWA-RD-03-081). Washington, DC: USDOT.

Flint Trading. (2005). DELTA Retrosign 4500 retroreflectometer for sign sheeting. Retrieved December 20, 2005, from http://www.flinttrading.com/?option=com_content&task=view&id=42&Itemid=58

Hawkins, H.G. , & Carlson, P.J. (2001, January). Results of visual evaluations of sign retroreflectivity compared to minimum retroreflectivity recommendations. Paper presented at the 80th Annual Meeting of the Transportation Research Board, Washington, DC.

Immaneni, V.P. , Hummer, J.E. , Rasdorf, W. , Yeom, C. , & Harris, E. (in press). Synthesis of sign deterioration rates across the US. Journal of Transportation Engineering.

Kirk, A.R. , Hunt, E.A. , & Brooks, E.W. (2001). Factors affecting sign retroreflectivity. Salem: Oregon Department of Transportation.

Kirtley, N. , & Rasdorf, W. (2001). Sign count approximation using field inventory sampling and calculated sign densities for NC primary routes. Raleigh: North Carolina State University, Department of Civil Engineering.

Lagergren, E.A. (1987). Traffic sign retroreflectivity measurements using human observers (WA-RD 140.1). Seattle: Washington State Department of Transportation.

10.

McGee, W.H. , & Paniati, J.A. (1998). An implementation guide for minimum retroreflectivity requirements for traffic signs. McLean, VA: USDOT.

11.

McGee, W.H. , & Taori, S. (1998). Impacts on state and local agencies for maintaining traffic signs within minimum retroreflectivity guidelines. Vienna, VA: BMI.

12.

Palmquist, M. , & Rasdorf, W. (2002). Sign count approximation using field inventory sampling and calculated sign densities: Analysis improvements, and methods . Raleigh: North Carolina State University, Department of Civil Engineering.

13.

Rasdorf, W. , & Hummer, J.E. (2004). Designing an efficient nighttime sign inspection program that ensures motorist safety [Research proposal]. Raleigh: North Carolina Department of Transportation.

14.

Rasdorf, W. , Hummer, J.E. , Vereen, S.C. , & Cai, H. (2005). A quantitative evaluation of the nighttime visual inspection method of sign evaluation. Journal of Transportation Research Forum, 44(1), 121-139.

15.

Vereen, S. , Hummer, J.E. , & Rasdorf, W. (2002). A sign inventory study to assess and control liability and cost (FHWA/NC/2002-17). Raleigh: North Carolina State University.

16.

Vereen, S. , Hummer, J.E. , & Rasdorf, W. (2004). Alternative approaches for state agencies to address the proposed minimum retroreflectivity standards. Journal of Public Works Management and Policy, 8(4), 235-248.