West of the camping area, the road is sealed as it climbs a tight, winding section up the mountain side.

The road passes through a historical single lane tunnel carved through the sandstone ridge in a forest area part way through the farmland section.

The tunnel is around 22 m long at ground level, but has a sandstone outcrop extending several metres further at its western end.

In August 1899 the local newspaper, Goulburn Evening Penny Post, described the progress of "work of tunnelling through the sandstone ridge at the gullies near Bullio is being rapidly pushed on by a gang of experienced men, who are using ratchet drills and other improved appliances, so that this portion of the work will be completed in about six weeks".

[8] The road was allocated Tourist Route 13, from its western end at Richlands to the turn-off to Wombeyan Caves during the 1990s and 2000s.

Hume Highway and Goulburn-Oberon Road via Goulburn are a better option if you are not aiming to get to somewhere between the Wombeyan Caves camping area and the sandstone tunnel west of High Range.

Please check on the status of the road before driving it as the portion down to and up from the Wollondilly River can often become extremely rutted and washed out, blocked by large fallen boulders or eroded so badly it becomes unpassable and is closed.