|Length:||15 miles (24.1 km)|
|Met:||A498, B4411, B4418 A499|
|Now part of:||A487|
|Route outline (key)|
The second incarnation of the A4085 was a cross-country road in Caernarfonshire, almost running from coast to coast.
The road started on the A498 at Tremadog and then headed north, keeping to the west of Snowdonia. It therefore started off by heading more-or-less westwards until it met the B4411 at Glan Dwyfach, after which it turned northwards. It continued on with the mountains to the right and flatter land to the left; there are also high hills in this direction but further away, allowing the road to follow relatively flat route. As the road continued north through Penygroes the A499 north coast road drew ever closer and the two roads finally met at Llanwnda, with the other road continuing north to Caernarfon.
The route described above was initially numbered B4410. The need for a flatter north-south A-road than the then-A487 through the Aberglaslyn Pass was soon understood and so the road was renumbered A4085 in 1935. The west coast trunk road was routed this way rather than along the A487 for obvious reasons and so in the 1960s reality caught up with numbering and the two roads swapped numbers, with the new A4085 taking the hilly road to the east. The present A487 follows more-or-less the same route as the old A4085 but there have been upgrades and much of the northernmost section of the road has been bypassed.