How can the newer pavement types be credited in the TNM?
TNM currently allows the user to select from 4 pavement types: DGAC, OGAC, PCC, and an average pavement type (combined DGAC and PCC). These data are based on measurements performed in seven States around the country. Incorporating new advanced pavement is possible, however future implementation will depend on FHWA policy, and a statistically sufficient amount of in-situ data measured using a consistent methodology. Current FHWA policy states, “Unless definite knowledge is available on the pavement type and condition and its noise generating characteristics, no adjustments should be made for pavement type in the prediction of highway traffic noise levels.” The use of a pavement type other than “Average” must be substantiated and approved by the FHWA, in advance of its use. “Future case” runs should also use average pavement unless otherwise justified.
