Document ID: chunk:federal_register_of_legislation:F2021C00509:reg:6:p3
Version: federal_register_of_legislation:F2021C00509
Segment Type: reg
Provision Reference: reg 6 (pt 3/10)
Character Range: 205610–208367

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 12 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 acoustica1ly reflective objects within this radius.
Figure l: Minimum requirements 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/d max)1/2

          where : d = square mesh sieve size, in mm
          d max = 8 mm for the mean curve
          d max = 10 mm for the lower tolerance curve
          d max = 6.3 mm for the upper tolerance curve

      Figure 2: Grading curve of the aggregate in the asphaltic mix with tolerances .

          In addition to the above, the following recommendations are given:
          The sand fraction (0.063 mm < square mesh sieve size < 2 mm) shall include