Section 6: Determining When To RestripeAnchor: #i1003814
Eventually all pavement markings degrade to the point where they reach the end of their useful service life. The end-of-service life of a pavement marking may be defined as the point when the marking has deteriorated so that it no longer provides suitable visibility to drivers. This end-of-service life, which may be anywhere from a few weeks to many years after placement of the marking, determines when the markings need to be restriped.
Because pavement marking visibility is critical at night, end-of-service life is often determined by nighttime visibility characteristics of the markings. The nighttime performance is then compared to the minimum amount of brightness that drivers need to safely navigate. Daytime performance evaluation measures also exist, but are not as critical.Anchor: #i1003829
Determining End-of-Service Life
TxDOT uses three methods for determining the end-of-service life of pavement markings:
- subjective daytime visual evaluation
- subjective nighttime visual evaluation
- retroreflectivity evaluation.
Explanations of each follow.
Subjective Daytime Visual Evaluation. Subjective daytime visual evaluation can be performed according to Test Method Tex-828-B under the section titled “Characteristics for Replacement Scheduling” using the daytime inspection method. This method involves determining the maximum daytime visibility distance of existing markings when viewed from a vehicle. Daytime visual inspection of pavement markings should occur at least once per year. Refer to the TxDOT Manual of Testing Procedures for detailed information.
Subjective Nighttime Visual Evaluation. Subjective nighttime visual evaluation can be performed according to Test Method Tex-828-B under the section titled “Characteristics for Replacement Scheduling” using the nighttime inspection method. This method involves determining the maximum nighttime visibility distance of existing markings when viewed from a vehicle with the headlamps on. Nighttime visual inspection of pavement markings should occur at least once per year. Refer to the TxDOT Manual of Testing Procedures for detailed information.
Retroreflectivity Evaluation. Retroreflectivity evaluation can be performed by taking a series of retroreflectivity measurements of the markings and comparing them to guidelines for minimum in-service retroreflectivity.Anchor: #i1003878
Minimum In-Service Retroreflectivity Guidelines
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.