This study was undertaken to provide much needed information on the uniformity of surface-course asphalt concrete being produced for paving projects under the auspices of the New York State Department of Public Works. Over a two-year period, 39 hot-mix plants were visited, and more than 500 hot-bin samples were obtained. The average gradation from each plant was used as a base from which to compute uniformity. The differences between average gradations and individual sample gradations were analyzed statistically to obtain an indication of the uniformity of asphalt concrete production on a statewide basis. From this study it was concluded that:

1. There is now available a realistic indication of the uniformity of top-course asphalt concrete being supplied to New York State highway projects.

2. None of the plants studied produced a mix which was extremely variable or exceptionally uniform.

3. Using statistical coefficients, as developed in this study, it is possible to establish tolerance limits which reflect the actual variations encountered in the production of asphaltic concrete.