The drive to Lake Onslow in the highlands of Central Otago is remote and spectacular. Take the Millers Flat Bridge from State Highway 6 over the Clutha River to Millers Flat. From there, head northwest on Teviot Road. Turn right into Oven Hill Road, then into Tima Burn Road. This well-maintained metal road climbs up the north side of the Lammerlaw Range to Lake Onslow Road at 698 metres. At various points, there are spectacular views across the highlands, the Teviot Valley, and the Garvie Mountains to the northwest.
Tima Burn Road starts well maintained, but the road deteriorates markedly from the turn-off to the south on Lake Onslow Road. There is a roadside warning sign. However, you can drive the road in standard cars in dry conditions, albeit there are some large ruts to avoid. It would be better to use a 4WD. There is also an exotic forest on this part of the route, another reason to be careful with the potential for forestry vehicles.
From the turnoff, the road continues to climb to a high point at 900 metres on the side of Mount Teviot (977 metres). From there, it drops down to Lake Onslow at 700 metres. There is a parking area near the dam, or continue on to park near the fishing cribs.
You can also access Lake Onslow Road from Roxburgh on Wright Road, then Saunders Road from Roxburgh, or Three Brothers Road from Teviot Road between Roxburgh and Millers Flat. Another option is to get there from Serpentine Flat to the northeast, along Deep Creek Road to the east end of Lake Onslow Road.
