Skip to main content

We are building a bypass from the Goat roundabout on the A499/A487 junction to the Plas Menai roundabout, around Llanwnda, Dinas, Bontnewydd and Caernarfon avoiding the town centres.

Under construction
Region / County:
north Wales
Start date:
early 2019
End date:
early 2022
£135 million
First published:
14 September 2017
Last updated:


Why we are we doing it

We want to: 

  • make it easier to travel without traffic jams
  • make it easier to travel between Llyn Peninsula, Porthmadog, Bangor and the A55
  • reduce noise and air pollution for people who live along the A487
  • make it safer for people to travel between towns
  • make it easier for heavy goods vehicles to travel in the area
  • make it safer to travel between Caernarfon, Bontnewydd by walking and cycling.

We want to prevent:

  • longer queues at the A499/A487 Goat roundabout
  • high volumes of vehicles passing through towns along this route
  • queues and delays on the A487, particularly at Eagles Junction, St David's and Morrisons roundabouts in Caernarfon, and at Plas Bereton.

Current progress

We have:

  • built 2 viaducts, over the Afon Seiont and Afon Gwyfrai,
  • started working on the 2 smaller bridges. For the first, which crosses the Welsh Highland Railway, concrete beams are now in position. On the second, we have built the reinforced walls and the bridge beams are now in position.

We are currently:

  • adding a fourth arm at Goat roundabout to connect the bypass with the A499 and A487
  • changing the Plas Menai roundabout to connect the bypass with A487 Felinheli bypass, Caernarfon road and the A487 into Caernarfon
  • building a safe crossing for cyclist, pedestrians and equestrians at the Goat roundabout to provide continuity with Lon Eifion and A487 Bontnewydd
  • building a walking and cycling route linking where the bypass crosses Bethel Road with a route to/from Bethel

We are also making space for wildlife and biodiversity along the road. This includes:

  • creating burrowing and foraging habitats for water voles
  • putting in a number of culverts to allow bats, fish and otters to cross the road
  • installing swift and dipper boxes on the two main viaducts
  • creating soft verges under one of the viaducts to allow wildlife to pass
  • installing amphibian-friendly drainage into road gullies
  • using a local seed source to plant flowers along the verges.


Public consultation exercise: 2010 to 2011
Preferred route announced: spring 2013
Appointment of contractor: end 2014
Site investigation and surveys: throughout 2015
Preliminary design: end 2015
Orders exhibition: autumn 2016
Public local inquiry: summer 2017
Start of bypass construction: early 2019
Bypass opening: early 2022

Next steps

Opening the bypass in early 2022.

We are also working with Gwynedd County Council to make the existing A487 through Caernarfon and Bontnewydd into a county road, once the bypass is opened.

What we are doing

We want to build 9.8km 2+1 carriageway - 2 lanes in one direction, 1 in the other, switching from one side to another between the Goat roundabout and Plas Menai roundabout. The route will:

  • create a western bypass to Llanwnda, Dinas and Bontnewydd
  • cross the existing A487 south of Caernarfon
  • cross Afon Seiont
  • pass south of the Cibyn industrial estate to form a junction with the A4086
  • cross the B4366.

It will involve constructing 22 structures including culverts and 7 bridges. The bridges will be:

  • a crossing over the Welsh Highland Railway
  • a 300m viaduct over Afon Seiont
  • a 280m viaduct over Afon Gwyrfai and its flood plains
  • 4 bridges carrying existing roads under or over the new road.

75% of the cost of the scheme will be spent with local Welsh suppliers.

We will also improve the existing A487 to improve existing junctions.

How we consulted

Four bypass options were presented to the public as part of a consultation exhibition in March 2010. 972 people attended these exhibitions and 498 completed questionnaires were received.                                         

The responses from these questionnaires demonstrated that the public was in favour of the bypass. Further consultations took place towards the end of the year before we announced our preferred route.

We had meetings with landowners, businesses and residents to understand the impacts of the scheme.

Latest announcements

Announcements and notifications


Reports, environmental statements and plans

Help and support

Ask a question about the project or report an issue


Balfour Beatty Jones Brothers (Ruthin) have a site office on Seiont Mill Road, Caernarfon LL55 2YL, open during normal business hours.

For appointments you can contact the Public Liaison Officer, on 07786 513571 or