5.2.5 Equivalent Heavy Vehicle (EHV(%))
The EHV(%) concept was developed to cater for the effects on sprayed seals of new types of heavy vehicles introduced in the last decade.
Heavy vehicles have a significant effect on aggregate packing and the performance of sprayed seals. The effect is exacerbated for very large heavy vehicles (LHV), i.e. Class 10 onwards which includes B‑doubles, double and triple road trains (Holtrop 2008). EHV(%) accounts for the large influence of the LHV portion of the traffic account on the performance of sprayed seals.
The EHV(%) is calculated in the seal design method using Equation 2. Austroads vehicle classes are provided in Appendix B:
| EHV(%) = SHV(%) + (LHV(%) x 3) | 2 | |||
| where | ||||
| SHV(%) | = | percentage of standard heavy vehicles in the traffic mix (i.e. Austroads vehicle Classes 3 to 9) | ||
| LHV(%) | = | percentage of large heavy vehicles in the traffic mix (i.e. Austroads vehicle Classes 10 and above) | ||
The value of EHV(%) calculated by this procedure is used solely for the determination of adjustments to the basic voids factor for the effects of traffic (Table 6.2) and does not alter the design traffic volume.
Designers must apply caution when designing binder application rates for seals used by these large heavy vehicles. They should monitor and compare their design against actual seal performance to provide additional information in order to be able to make appropriate additional amendments for traffic adjustments in future designs. Refer to Appendix C for some worked examples on converting heavy vehicle traffic counts to EHV(%).