A487 Caernarfon to Bontnewydd Bypass

Scheme outline

Construction of a new bypass to carry the A487 around Caernarfon and the adjacent villages of Llanwnda, Dinas and Bontnewydd. The new road will run from the Plas Menai Roundabout north of Caernarfon to the Goat Roundabout with the A499 south of Llanwnda, with two intermediate junctions in the form of flat roundabouts to connect with the A4086 Llanberis Road and the A487 north of Bontnewydd.

The new road will be 2+1 standard, meaning it will be a single carriageway with a total of three lanes, with one running lane in each direction and a third overtaking lane that will switch directions periodically. This design will allow regular overtaking opportunities in both directions without the expense of building a full dual carriageway. On some approaches to roundabouts, depending on the configuration of the three lanes, short sections of dual two-lane road will be provided as a transition between the junction and the three-lane layout. The middle overtaking lane will only be available for use by traffic in one direction at any particular point.

As well as relieving Caernarfon town centre from through traffic and opening up access to the coast and countryside south of the town, the bypass will also relieve nearby local roads that are presently used as an informal bypass by unsuitably heavy volumes of traffic.

Under construction
Bypass or realignment
for use by all traffic
Highway authority
Welsh Assembly Government


24 May 2018

The bypass has been given the go-ahead with contracts to be awarded in June and work expected to start in November.

19 December 2018

Construction of the bypass has been awarded to Balfour Beatty and Jones Bros. Preparatory work is underway with construction expected to begin in winter 2018/19.

2 March 2019

Work has started on this scheme.

20 April 2019

Most tree felling and hedge clearance appears to be complete where the new route and existing A487 meet.

More information


With thanks to Gerry McKenna for information on this page.