Evaluation and Analysis of LTPP Pavement Layer Thickness Data

Figure 73 in page 120 shows the results of one-sided t-tests with 95 percent confidence level on whether the absolute differences between as-constructed (core-measured) and as-designed thicknesses are below, within, or above the tolerance level (TV) of 6.35 mm. A chart is presented for the percentage distribution of the absolute differences for five material types including DGATB, LC, PATB, PCC, and SB from the corresponding target thickness listed in Table 64 in page 118. The percentage is determined by the number of sections with the absolute differences below, within, or above the tolerance level (TV) of 6.35 mm divided by the total number of sections for the corresponding target thickness. The horizontal axis of the chart is the corresponding target thicknesses for each of the five material types. The vertical axis is the percentage of the absolute differences that are below, within, or above the TV of 6.35 mm, which are displayed as a vertical bar of 100 percent in total, consisting of black (below the TV of 6.35 mm), blank (within the TV of 6.35 mm), and gray (above the TV of 6.35 mm) percentages. On average for the five material types, about 9.9 percent of the absolute differences are below the TV of 6.35 mm; about 64.6 percent of the absolute differences are within the TV of 6.35 mm; and about 25.5 percent of the absolute differences are above the TV of 6.35 mm.

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