Document ID: chunk:federal_register_of_legislation:F2021C00509:front:0:p30
Version: federal_register_of_legislation:F2021C00509
Segment Type: other
Provision Reference: 
Character Range: 88095–91066

absorption:
             When the surface is new;
               if the surface meets the requirements when new, no further periodical testing is required. If it does not meet the requirement when it is new, it may do later because surfaces tend to become clogged and compacted with time.
            (b) For texture depth (TD):
             When the surface is new;
               When the noise testing starts (NB: not before four weeks after laying);
               then every twelve months.

           3. Test surface design

           3.1. Area

            When designing the test track layout it is important to ensure that, as a minimum requirement, the area traversed by the vehicles running through the test strip is covered with the specified test material with suitable margins for safe and practical driving. This will require that the width of the track is at least 3 m and the length of the track extends beyond lines AA and BB by at least 10 m at either end. Figure 1 shows a plan of a suitable test site and indicates the minimum area which shall be machine laid and machine compacted with the specified test surface material. According to annex 3, paragraph 3.1.1.1, measurements have to be made on each side of the vehicle. This can be made either by measuring with two microphone locations (one on each side of the track) and driving in one direction, or measuring with a microphone only on one side of the track but driving the vehicle in two directions. If the former method is used, then there are no surface requirements on that side of the track where there is no microphone.
           NOTE--There shall be no large acoustically reflective objectss within this radius.

Figure 1.
Minimum requirement for test surface area.
The shaded part is called "Test Area."

           3.2. Design and preparation of the surface

           3.2.1. Basic design requirements
            The test surface shall meet four design requirements:

           3.2.1.1. It shall be a dense asphaltic concrete.

           3.2.1.2. The maximum chipping size shall be 8 mm (tolerances allow from 6.3 to 10 mm).

           3.2.1.3. The thickness of the wearing course shall be > 30 mm.

           3.2.1.4. The binder shall be a straight penetration grade bitumen without modification.

           3.2.2. Design guidelines

            As a guide to the surface constructor, an aggregate grading curve which will give desired characteristics is shown in Figure 2. In addition, Table 1 gives some guidelines in order to obtain the desired texture and durability. The grading curve fits the following formula:
                     P (% passing) = 100(d/dmax)1/2
                     where:
                     d = square mesh sieve size, in mm
                     dmax = 8 mm for the mean curve
                     dmax = 10 mm for the lower tolerance curve
                     dmax = 6.3 mm for the upper tolerance curve

Figure 2.
           Grading curve of the