Refer to the Mt Arrowsmith parent page
From the parking spot at km 13.3 on Pass Main walk a few metres back down the road and up the fourth logging road spur. It’s well flagged.
The spur road is getting progressively washed out but if you have a high slung 4x4 and don't mind beating it up a little, the spur can be driven to within ~100 metres of the trailhead. Park at the obvious BIG washout.
Pass Main Spur to the Judges Route
Judges Route in May
Descending the Judges Route
Follow the well marked trail generally northeast to the summit steeply but with little real difficulty and only one or two bits of minor exposure. The trail is maintained only on a volunteer basis and consequently is becoming eroded in some of the higher, open sections as people choose their own route. Footing can be loose on the descent. This is the only route to the summit of Arrowsmith when a rope need not be carried – not to mention used – by most parties.
An ascent on snow in early season (April/May) or in winter will avoid the loose/scree sections. My vote on route quality above is based upon doing it on snow. On dirt it's down to 2 stars.
The route was named by one of the first ascensionists, Ralph Hutchinson, who was contemplating whether or not to accept a judgeship at the time.
None in summer. Ice axe and crampons in winter and spring or whenever the route is under snow.