An Analysis of In-Service Type III High Intensity Traffic Sign Retroreflectivity and Deterioration Rates in Texas

摘要

Roadway traffic signs are a fundamental medium for conveying critical information to the roaduser and 2009 MUTCD has set minimum retroreflectivity requirements for traffic signs. Signmanagement strategies based on service life are one approach for meeting sign compliance.Generating deterioration rates and prediction models from a sample of infield sign measurementsis one method for establishing expected service life. In 2009, researchers collected a sample of859 Type Ⅲ retroreflectivity signs in seven different regions of Texas. The objective of thiseffort was to generate prediction models and deterioration rates from the Type Ⅲ sign data. Theoverall sign sample compliance was 99 percent and the observed likelihood of failure was 2percent for signs between 10 and 12 years of installation and 8 percent for signs 12 to 15 years.The linear prediction models revealed that there were differences in deterioration rates amongthe regions. The differences ranged from -2 to -8 cd/lx/m~2 per year for white sheeting and -1 to -12 cd/lx/m~2 per year for yellow sheeting. Models exhibited poor correlation between predictedand measured values and the R-squared ranged from 0.10 to 0.30. Despite the weakrelationships, the models revealed insightful trends and provided a broad perspective ofTxDOT's current sign practices. Deterioration rates and prediction models can be valuablecomponents to a comprehensive and integrated sign maintenance program, but they do not bythemselves ensure sign retroreflectivity compliance or dictate definite sign replacement periods.