5.2.7 Access Roads to Sites such as Quarries and Mining Locations
Traffic in these locations often consists predominantly of SHV and LHV with only a few light vehicles and cars. In such circumstances, the determination of an appropriate traffic volume for selection of the basic voids factor at the start of the design process can be difficult.
Adjustments to binder application design rates for proportions of equivalent heavy vehicles greater than 15% and up to 65% of total traffic are provided in Table 6.2 for single/single seals. Where the proportion of equivalent heavy vehicles is greater than 65%, the following procedure may be used for selection of an alternative basic voids factor.
The procedure is based on the assumption that the basic voids factors shown in Figure 6.1 and Figure 6.2 have been developed around a mixture of light and heavy vehicles, where the proportion of heavy vehicles (including SHV and LHV) is typically around 10% of the total. In order to use the same procedure when EHV(%) exceeds 65%, it is appropriate to determine a nominal design traffic volume that adequately accounts for the influence of the high proportion of heavy vehicles.
The nominal design traffic for access roads is determined by Equation 3:
|Nominal design traffic volume for access roads = (SHV + LHV\( \times\) 3) \(\times\) 10 + volume of light vehicles||3|
|SHV||=||number of standard heavy vehicles in the traffic mix (i.e. Austroads vehicle Classes 3 to 9)|
|LHV||=||number of large heavy vehicles in the traffic mix (i.e. Austroads vehicle Classes 10 and above)|
|Volume of light vehicles||=||number of light vehicles in the traffic mix (i.e. Austroads vehicle Classes 1 and 2)|
The procedure is as follows:
- Determine number of SHV, LHV and light vehicles.
- Calculate Equation 3 to determine a nominal design traffic volume.
- Select a basic voids factor based on this nominal traffic volume.
When using this procedure, adjustment to the basic voids factor from traffic effects should be applied using the 0 to 15 EHV(%) category of Table 6.2, which accounts for channelised traffic and slow-moving vehicles.