Date of Award:

12-2012

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Advisor/Chair:

Kevin Heaslip

Abstract

Since the establishment of the first minimum retroreflectivity levels in 1993, agencies and researchers have focused on determining the service life of different sheeting type and color combinations. While deterioration curves and measured retroreflectivity are viable methods for maintaining retroreflectivity compliance, they do not ensure the ability of the traffic sign to convey its intended message. Retroreflectivity efficiency only ensures visibility but does not properly describe the legibility of the sign. Therefore, while agencies across the nation are developing and implementing traffic sign maintenance plans, the emphasis should not be solely placed on visibility.

In order to evaluate the performance of UDOT’s traffic signs, a sample sign population was collected across all four of UDOT’s maintenance regions. Analysis on this sample set not only determined the current rate of compliance, but it also identified several issues seen throughout the population. Signs under UDOT’s jurisdiction are four times more likely to have substantial damage to the sign face than to fail to meet the minimum retroreflectivity levels. Analysis was conducted on determining contributing factors damage rates and it was determined that precipitation, elevation, seasonal temperature swing, and exposure of the sign all contributed to higher rates of damage. Additional analysis was conducted on determining the service life of different type and sheeting combinations. Hindered by the lack of known installation information, the analysis only identified service life as a significant contributor to sheeting deterioration.

Since the majority of new sign installations are prismatic sheeting, the recommended maintenance plan needs to reflect the performance characteristics of this sheeting while continuing to manage the existing sign population. With the combination of UDOT’s current sign knowledge and the sheeting deterioration and damage analysis conducted in this thesis, the feasibility of the five preapproved FHWA methods is discussed. This report concludes with the recommendation of a visual nighttime inspection method due to this method’s ability to assess both the visibility and legibility of traffic signs. This will ensure that UDOT maintains compliance with the retroreflectivity mandate, while improving safety for motorists.

Comments

This work made publicly available electronically on December 20, 2012.

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