The

Texas Manual on Uniform Traffic Control Devises

(TMUTCD) requires that all pavement markings be retroreflective if they are to be visible at night. At present, no numerical values are associated with this requirement; however, minimum retroreflectivity standards are currently in development by the FHWA, as directed by the United States Congress.

As a result of this directive, the FHWA has developed draft recommendations for minimum levels of in-service retroreflectivity for pavement markings. These draft recommendations currently do not constitute a standard and exist for purposes of providing guidance to agency personnel. It is not yet known when nationwide compliance with federal minimum retroreflectivity standards will go into effect, although many state transportation agencies have already begun monitoring the retroreflectivity of their pavement markings. Establishment of minimum standards will occur through the federal rulemaking process.

Suggested Minimum Value.

Based on the FHWA draft recommendations, TxDOT has suggested that as a rule-of-thumb, average pavement marking retroreflectivity values of 80–100 mcd/m2/lux measured with a 30 meter geometry retroreflectometer indicate that markings should be considered for replacement. Note that retroreflectivity levels shown here are for guidance purposes only and are subject to change. Where additional roadway visibility is provided at night by retroreflective raised pavement markings or continuous roadway lighting, lower retroreflectivity levels may be acceptable. Pavement marking retroreflectivity under wet conditions is often much lower than during dry conditions. Retroreflective raised pavement markings are provided on most TxDOT roadways to improve visibility under wet conditions.

Locations for measurement of in-service retroreflectivity should be selected based on those sections where markings display poor nighttime visibility observed during nighttime inspections. Remember that retroreflectivity is only one of several factors to consider when determining whether or not markings should be replaced.