Technical information

2-3
1.7% to 4.9% (average of 3.1%). Standard tires were used (Priest et al., 2005) identified
as 275/80R22.5 and inflated to 100 psi.
Figure 2.1.2: Photograph of a typical NCAT truck (Priest and Timm, 2006).
Table 2.1.1: Breakdown of axle properties for an ‘average’ NCAT truck (Priest and
Timm, 2006).
Axle-name Steer Drive Trailer
Axle-
Number
1S 1D 2D 1T 2T 3T 4T 5T
Axle-type
Single-
Axle
Tandem-Axle
Single
-Axle
Single-
Axle
Single
-Axle
Single
-Axle
Single
-Axle
No. of
Wheels
2 4 4 4 4 4 4 4
Average
Axle-Load,
lb (kg)
10,680
(4,850)
20,320
(9,225)
20,290
(9,210)
21,010
(9,540)
20,760
(9,425)
21,310
(9,675)
20,550
(9,330)
20,613
(9,360)
COV for 5
Trucks
3.9% 3.9% 4.9% 2.2% 2.5% 1.7% 3.6% 2.2%
2.2 CONSTRUCTION OF TEST SECTIONS
2.2.1 Pavement Structures
Pavement structures in the NCAT ‘structural study’ were designed using the 1993
AASHTO guide employing three different traffic levels. The final outcome is shown in
Figure 2.2.1. It may be seen that each structure includes 6 in. (152 mm) of unbound
granular base under HMA layers of varying thickness having different composition
and/or binder grade. Both N1 and N2 sections were designed with 5 in. (127 mm) of
HMA, sections N3 and N4 were designed with 9 in. (229 mm) of HMA, and sections