Pavement marking materials provide positive guidance to the travelling public, in the form of lateral positioning, messages, and nighttime visibility of the road geometry. They are a form of "traffic control device" as defined by the MUTCD. It is understood that their level of service, as a function of quality and durability, should be maintained at consistent levels for adequate operational performance of the road facility.
There are many different types and classes of pavement marking products available today. Each is manufactured with differing formulas specific to the class of product, pavement surface application, and a host of other significant factors, An individual brand of pavement marking material can have several different formulations with alterations made for a specific use or user specification.
This inherent variability within a dynamic industry and the need to compare product performance on an even playing field led to the adoption of ASTM Specification D 713, the Accelerated Wear Test, by AASHTO's NTPEP Oversight Committee. This procedure allows over 200 similar products to be tested at once, side by side, and in the same conditions by applying the pavement marking materials transverse to the direction of traffic across the roadway in what is called a "testing deck". The testing deck ensures that products are exposed to equal amounts of wear generated by the continuous flow of traffic across the deck, as well as the same environmental stresses for the entire evaluation. A series of instrumented and observational field measurements are made at specific intervals for each product being evaluated and performance results are determined for reporting.
Each year, NTPEP conducts Accelerated Wear Test evaluations of pavement markings in different zones defined by AASHTO to represent various geographical and climatic regions. Starting each spring, manufacturers are asked to submit each individual product they would like to have NTPEP tested and certified. Depending on the type of pavement marking, the product is subjected to a 1-year, 2-year, or 3-year field test, and depending on the class of the pavement marking, a series of applicable laboratory tests. Results are reported through the NTPEP Datamine website. NTPEP reports are available to other AASHTO committees including: Traffic Engineers, Maintenance Engineers, Materials Engineers, and Chief Engineers.
The NTPEP Technical Committee is responsible for developing a "Project Work Plan" each year that defines the evaluation protocol for each pavement marking material type. During the annual working meeting, the previous year's project work plan is discussed, changes are made, and the work plan is balloted for approval from two thirds of the 52 AASHTO voting members of each state department of transportation (DOT). Improvements and changes are implemented immediately for the next testing cycle. This allows the NTPEP program to remain effective and efficient by having the ability to quickly adapt to the needs of both the manufacturers and users through the dynamic nature of the NTPEP process.