Be very careful if using an area to which other vehicles have "unfettered access". Many sections of the Road Traffic Act (including those covering licence and insurance requirements) apply to roads or "other public places". There is no legal definition of "other public places" but generally if other drivers can drive their vehicles there it will be considered as such.
Even if the area is not subject to compulsory insurance for vehicles, if damage or injury is caused to a Third Party the driver, or owner, or landowner may be liable if neglience is proved.