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We are proposing to build 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.

First published:
14 September 2017
Last updated:


Project status: in construction
Region/county: north Wales
Start date: early 2019
End date: early 2022
Cost: £135m
Employers agent: EC Harris, Ramboll
Design and build contractors: Balfour Beatty, Jones Brothers (Ruthin)
Designers: WSP and Parsons Brinckerhoff, TACP

Why we are doing it

We want to address the following issues:

  • traffic volumes are growing which causes traffic congestion and increases journey times
  • the road infrastructure provides a poor connection to Bangor and the A55. This might hinder economic development
  • noise and air pollution affects the quality of life for residents along the A487 with the high volumes of traffic.

There are also many collisions in these urban areas. Heavy goods vehicles access the Cibyn industrial estate and vehicles travel too fast Vehicles use unsuitable country roads to bypass the A487.

We find it difficult to maintain this road due to high volume of traffic and there aren’t any alternative routes.

If we don’t take action we predict that traffic flow will increase and cause the following problems:

  • 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.

A WelTAG Stage 1 Appraisal was undertaken in 2008. From this, 4 options for improving traffic in the area were considered:

  1. A new bypass Llanwnda to Plas Menai.
  2. 'Local' bypasses for Dinas, Bontnewydd, Pont-rug, Crug and a new link to the Cibyn industrial estate.
  3. Standard rail provision.
  4. A package of measures to include:
    • road traffic management
    • parking
    • accident prevention
    • improving bus services
    • cycle and pedestrian areas
    • crossings

In 2009 we appointed Parsons Brinckerhoff and TACP to complete the WelTAG Stage 2 appraisal. This involved looking at the 4 bypass options. The 4 routes along with 7 suggested by the public underwent a detailed appraisal including whether they were feasible taking in to account a number of factors.

We announced the purple option as the preferred route in November 2010. With budget pressures we carried out a review of options and withdrew our original preferred route. We then announced the yellow option as the preferred route.

The contract for the project was awarded to Balfour Beatty and Jones Brothers (Ruthin) in winter 2014. They will be supported by WSP Parsons Brinckerhoff and TACP as their technical and environmental advisors.

The scheme proposals were developed in consultation with stakeholders and public information exhibitions were held in spring 2015.

We published draft Orders, the environmental statement and other associated reporting in summer 2016 and held public exhibitions that autumn to explain our proposals.

A public inquiry was held over the summer of 2017 and the Inspector closed the inquiry in writing in August 2017.

Current progress

Our contractors are currently designing and constructing the bypass. We began site clearance in February 2019 and have completed the majority of the site clearance and fencing works along the length of the scheme. We have started the earthworks operations near the Goat and Plas Menai roundabouts.

The plan

The scheme is being developed to meet 5 objectives:

  • reduce journey times between Llanwnda and Plas Menai
  • reduce journey times between Llanwnda and Caernarfon
  • reduce the number of vehicles passing through residential communities including Llanwnda, Dinas, Bontnewydd and Caernarfon
  • reduce accidents on the A487
  • improve resilience on this network

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.


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

How we are consulting

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.


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, Bryn Williams, on 07786 513571. For further information on the scheme contact Balfour Beatty Jones Bros (Ruthin).