Document ID: chunk:federal_register_of_legislation:F2021C00509:front:0:p48
Version: federal_register_of_legislation:F2021C00509
Segment Type: other
Provision Reference: 
Character Range: 138969–141736

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 reflecting products within this radius.
  Figure 1: 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/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 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 < 2mm) shall include no more than 55% natural sand and at least 45% crushed sand;
         The base and sub-base shall ensure a good stability and evenness, according to best road construction practice;
         The chippings shall be crushed (100% crushed faces) and of a material with a high resistance to crushing;
         The chippings used in the mix shall be washed;
         No extra chippings shall be added onto the surface;
         The binder hardness expressed as PEN value shall be 40-60, 60-80 or