To calculate the annual straight-line depreciation expense, we first need to determine the depreciable amount.
\begin{aligned} \text{Depreciable amount} &= \text{Cost of the vehicle} - \text{Salvage value} \ &= R170000.00 - R20000.00 \ &= R150000.00 \end{aligned}
Next, we calculate the annual straight-line depreciation expense:
\begin{aligned} \text{Annual Depreciation Expense} &= \frac{\text{Depreciable amount}}{\text{Useful life}} \ &= \frac{R150000.00}{5} \ &= R30000.00 \end{aligned}
Therefore, the annual straight-line depreciation expense for the vehicle is $\boxed{R30000.00}$.