Section 6: Retroreflectivity Performance Specifications for ContractsAnchor: #i1021754
Final contract acceptance is a quality-assurance measure that involves inspecting the markings a certain amount of time after all markings have been placed to ensure long-term performance. Retroreflectivity performance-based pavement marking contracts have been used successfully in other states for years as a final acceptance measure. Such contracts are attractive because they shift specifications away from the traditional recipe process to an objective performance process, placing greater responsibility on contractors and manufacturers. In addition, retroreflectivity measurement provides a numeric comparison of how efficiently a marking returns light to the driver’s eyes, thereby reducing the subjectivity that exists when performing nighttime visual evaluations.
Final acceptance for TxDOT pavement marking contracts is usually based on whether the markings meet a specified minimum level of retroreflective performance. Compliance is often determined by a series of retroreflectivity measurements, which are taken a specified number of days after placement of the markings to allow for removal of loosely adhered glass beads. The purpose of using retroreflectivity measurements for final acceptance is to provide a reasonable amount of assurance that newly applied markings will meet or exceed service life expectations.Anchor: #i1021769
All retroreflective performance specifications include three important factors:
- minimum retroreflectivity values
- timing of measurements
- number of measurements.
Basis for Specification Compliance
Upon collection of retroreflectivity data, compliance with the specification is usually based on both of the following:
- The retroreflectivity average for a given pavement marking section is greater than the specified minimum value.
- The percentage of measurements that are less than the specified minimum retroreflectivity value for a given pavement marking section is below the specified minimum percentage.
The final acceptance period and performance of the corresponding retroreflectivity measurements should be in accordance with TxDOT specifications. Test Method Tex-828-B should only be used as a guide in determining the nighttime brightness and appearance of the markings, not for final acceptance purposes.