Since Standard Specification Item 316 already allows transverse variation in asphalt rate, it is only necessary to insert a note in the plans that invokes and further defines this requirement. The recommended plan note is:�

“In addition to other asphalt distributor requirements, the asphalt distributor shall be capable of providing a transversely varied asphalt rate. The Contractor shall demonstrate that the distributor can apply an asphalt rate outside of the wheel path locations between 22 and 32 percent higher than the asphalt rate being applied in the wheel paths. The contractor’s calibration of the distributor will include verification of this capability and a description of the spray bar(s) and nozzles to be used. The percentage difference in asphalt rate provided by each tested spray bar and nozzle arrangement shall be provided to the Engineer. The Engineer will select the pavements where the transversely varied asphalt rate is to be provided.”�

Requiring that contractors be able to provide at least one TVAR between 22 and 32 percent should allow every contractor to meet this requirement by using differing standard nozzle sizes across a single spray bar. A study of nozzle sizes conducted in the Brownwood District determined this percentage range.�

Some contractors have distributors with dual spray bars and separate computer controllers. These contractors have the ability to vary asphalt rates over a much broader range than that suggested for the plan note.�