#REDIRECT [[A roads in Zone 4 of the Great Britain numbering scheme]]
The '''A4085''' is a 20 mile road between [[Caernarfon]] and [[Penrhyndeudraeth]] in [[North Wales]] that runs through the scenic [[Aberglaslyn Pass]].
The road begins at the southern apex of a triangular one way system in [[Caernarfon]] on the [[A487 road|A487]]. It heads south signposted for [[Beddgelert]]. As it leaves Caernarfon it passes the site of the Roman Legionary fort [[Segontium]] and later crosses the Afon Seiont and the course of the Caernarfon to Llanberis railway. After 1.5 miles it crosses a roundabout at Caeathro. The road as far as Waunfawr is reputed to be a Roman Road and is fairly straight. After Waunfawr the road joins the Gwyrfai Valley, a glaciated U shaped valley along the west side of [[Snowdon]]. At various places along the valley it crosses and recrosses the [[Welsh Highland Railway]]. The road passes along the east shore of Llyn Qwellyn (Caernarfon's water supply), before climbing to a summit just south of [[Rhyd Ddu]]. The Welsh Highland Railway is under construction south of here towards Porthmadog and various works and construction trains can be seen alongside the road.
The summit of the pass is at Pitt's Head and then the road and railway drop to [[Beddgelert]] and the [[Aberglaslyn Pass]], where the road multiplexes with the [[A498 road|A498]]. The A4085 is the major road at the junction.
[[Image:Open_top_bus.jpg|right|thumb|The A4085 carries an open topped bus service in school holidays from Easter to the end of August to provide a link to the WHR at Rhyd Ddu. B.W.Hughes ]]
The railway can be seen again in the Aberglaslyn Pass on the east bank of the Afon Glaslyn, while the road continues along the west bank . The A4085 road diverges to the left at Pont Aberglaslyn before taking a curvacous route mostly following old seacliffs of the Afon Glaslyn estuary. It passes under the Welsh Highland Railway again at Nantmor. After Garreg, the road climbs over a hill and crosses the [[Ffestiniog Railway]] by level crossing. It then takes a narrow curvaceous descent through Penrhyndeudraeth to rejoin the A487 at the cross roads in the middle of the village.
== History ==
The road was created from early [[toll road]]s. The toll road between Pont Cae'r Gors and a point a mile to the south followed an easier 1 in 20 gradient than the steep farm track to the west that preceeded it. There was some improvement in the 1960s/70s halfway between Pont Aberglaslyn and Garreg and in 2005 nearer to Garreg. Just south of the Goat Hotel in Beddgelert is an arched railway overbridge (with height and width restrictions) built by the [[Porthmadog, Beddgelert and South Snowdon Railway]] but never used.
==External link==
*[http://www.isengard.co.uk/ Rebuilding The Welsh Highland Railway - Barrie Hughes]
