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Sir Fynwy
Location Map ( geo)
Monmouthshire Flag.png
Cameraicon.png View gallery (11)
Primary Destinations
Abergavenny • Chepstow • Cwmbran • Monmouth • Newport
Other Important Destinations
Current Highway Authorities
Blaenau Gwent • Caerphilly • Cardiff • Monmouthshire • Newport • Torfaen
Brecknockshire • Glamorgan • Gloucestershire • Herefordshire
Welsh Government Roads
M4 • M48 • A40 • A48(M) • A449 • A465 • A466 • A4042
This article is about the County.
For the Highway Authority, see Monmouthshire Council

OS 1939 Ten Mile Road Map showing Monmouthshire in England

Monmouthshire (Sir Fynwy in Welsh) is a traditional county in south-east Wales. Historical reasons – chief among them the inclusion of the county in the Oxford circuit of the English Assizes – led at one time to the indication of Monmouthshire as part of England on some maps (such as, for example, the OS Quarter Inch 5th Series); the county was only situated firmly in Wales in law in 1974. Although the county town is Monmouth the county council was based in Newport.

The county council was abolished in 1974; the county was then administered by Gwent (which had more-or-less the same boundaries) until 1995 when Monmouthshire County Council was reinstated. However, the revived area only covers the eastern two-thirds of the county, with the remainder split amongst another few administrative areas.

Geography & Economy

Brynglas Tunnels

Monmouthshire runs east-west between the Rivers Wye and Rhymney and north-south between the Black Mountains and the Bristol Channel. The eastern half is largely rural whilst further west the county moves into the industrialised valleys of South Wales. The county is likewise split regarding industry, with agriculture prevailing in the east and coal mining in the west. The latter has now ceased, as has the steel industry centred on Ebbw Vale. Monmouthshire is not known for its coastline; only Newport and Chepstow have been ports and the county has no seaside resorts.


The A466 by Tintern Abbey

Monmouthshire has perhaps the best road network of any Welsh county; the problems caused by mountainous terrain elsewhere in the county do not apply here. However, there is no specific focus of the county's roads; although the main population centres of Abergavenny, Monmouth and Newport do have a number of roads radiating from them, all are close to the county's borders and so only form a local focus. All of Wales's motorways run through Monmouthshire: the M4 enters the county from England across the Second Severn Crossing and the M48 across the Severn Bridge and Wye Bridge; the A48(M) is a short link providing access into Cardiff from the east. The motorways are managed by the South Wales Trunk Road Agent, as are the county's other trunk roads: the A40 and A465 run east-west of the north of the county, the A4042 and A449 link these roads to the M4, and the A466 provides access to Chepstow. Non-trunk roads in the rural east of Monmouthshire are maintained by Monmouthshire County Council. Five other principal area authorities, each with its own highway department, fulfil the same role in the western half of the county. They are Blaenau Gwent CBC, Caerphilly CBC, City of Cardiff Council, Newport City Council and Torfaen CBC.

The Newport Transporter Bridge across the River Usk to the south of Newport is the only one of its kind in Wales. The Newport Southern Distributor Road (A48) now crosses the river nearby, leaving the transporter bridge to local traffic and enthusiasts. To the north of Newport, the Brynglas Tunnels on the M4 are a major bottleneck and cannot be widened. There have at various times been plans to bypass the area entirely by the building of a new motorway to the south of Newport, although the most recent plans were shelved in 2019.

Route From To Length
M4 Chiswick, Middlesex Pont Abraham, Carmarthenshire 191.9 miles View
M48 Tockington Llanfihangel Rogiet 13 miles View  
A48(M) Castleton St Mellons 2.2 miles View
A40 London Fishguard 263 miles View
A48 Highnam, Gloucester Carmarthen 119 miles View
A437 Highnam, Gloucester Newport 41 miles View
A449 Stafford Coldra, Newport 108 miles View
A455 Coldra Newport 4.2 miles View
A465 Neath Bromyard 79.3 miles View
A466 King's Thorn Chepstow Interchange 30 miles View
A467 Newport Brynmawr 20.8 miles View
A468 Bassaleg Nantgarw 11.9 miles View
A469 Roath, Cardiff Bute Town 24.5 miles View
A471 Abergavenny Usk 11 miles View
A472 Usk Abercynon 23.7 miles View
A4042 Newport Abergavenny 18.2 miles View
A4043 Blaenavon Pontypool 6.0 miles View
A4044 Crumlin Brynmawr 10.0 miles View
A4046 Aberbeeg Bryn-Serth 7.6 miles View
A4047 Tredegar Brynmawr 4.1 miles View
A4047 Ebbw Vale Waun-y-Pound 0.5 miles View
A4048 Pontllanfraith Tredegar Junction, Nant-y-bwch 11.2 miles View
A4049 Bryn Tir Phil 6.5 miles View
A4050 Pengam Tir-Phil 5.3 miles View
A4051 Newport North Cwmbrân 6.6 miles View
A4052 Cardiff Road Watch House Parade 0.9 miles View
A4072 Tredegar Park Rogerstone 3.0 miles View
A4125 Little Mill Abergavenny 6.8 miles View
A4136 Huntley Monmouth 16.6 miles View
A4143 Llanfoist Abergavenny 0.7 miles View
A4232 Cardiff West Cardiff Gate 17.8 miles View
A4281 Victoria Ebbw Vale East and West junctions View
A4810 Magor Liswerry 5.5 miles View   
B4004 Coldra Newport 4.2 miles View
B4223 Monmouth Huntley 16.6 miles View
B4232 Monmouth King's Thorn 12.6 miles View
B4233 Abergavenny Monmouth 14.2 miles View
B4234 Raglan Llanvihangel Gobion 4.5 miles View
B4235 Usk (E) Chepstow 11.7 miles View
B4236 Llanyrafon, Cwmbrân The Coldra, Newport 5.2 miles View
B4237 Maes-glas Coldra 5.0 miles View
B4237 Maindee Newport Docks 2.7 miles View
B4238 Commercial Street High Street 0.4 miles View
B4239 Rumney Maes-glas 9.4 miles View
B4239 Alexandra Road Transporter Bridge 0.2 miles View
B4240 Cardiff Road, Newport Risca Road, Newport 0.5 miles View
B4241 Harlequin Roundabout Risca Road 1.3 miles View
B4242 Bassaleg Tredegar House 1.0 mile View
B4243 Bassaleg Rogerstone 1.7 miles View
B4244 Pontypool Llantarnam 5.6 miles View
B4245 Langstone Parkwall Roundabout 9.9 miles View
B4245 Little Mill Abergavenny 6.8 miles View
B4246 Pontnewynydd Abergavenny 12.8 miles View
B4247 Blaenavon Govilion 4.4 miles View
B4248 Blaenavon Brynmawr 4.5 miles View
B4249 Antwerp Place Somerset Street 0.6 miles View
B4250 Newbridge Abercarn 1.4 miles View
B4251 Wattsville Crumlin 11.3 miles View
B4252 Pengam Maesycwmmer 1.8 miles View
B4253 Blackwood Pengam 1.4 miles View
B4254 Edwardsville Blackwood 6.2 miles View
B4256 Tredegar Rhymney 3.0 miles View
B4257 Pontlottyn Llechryd 3.1 miles View
B4269 Llanfoist Llanellen 1.9 miles View
B4288 St Mellons Pentre-poeth, Bassaleg 5.3 miles View
B4293 Monmouth Chepstow 16.2 miles View
B4347 Vowchurch Rockfield 19.1 miles View
B4423 Llanvihangel Crucorney Llanthony 6.1 miles View
B4458 Monnow Street St James's Street 0.2 miles View
B4471 Hafodyrynys Aberbeeg 3.2 miles View
B4472 Cwm-dows Crumlin 1.2 miles View
B4477 New Tredegar Rhymney 3.0 miles View
B4478 Willowtown Briery Hill 1.4 miles View
B4487 Roath St Mellons 4.3 miles View
B4490 Crosskeys Risca 1.4 miles View
B4511 Aberbargoed Argoed 2.0 miles View
B4521 Abergavenny Old Pike, Peterstow 18.9 miles View
B4560 Beaufort Talgarth 16.8 miles View
B4562 Llanishen St Mellons 5.0 miles View
B4591 Maindee, Newport Abercarn 10.6 miles View
B4596 Newport Caerleon 2.5 miles View
B4598 Abergavenny Usk 9.7 miles View     
T10 London Fishguard View
T17 Newport Shrewsbury View
T76 Neath Abergavenny View
T77 Raglan Llandovery View
T78 Newport Worcester View
T103 Coldra Tredegar Park 6.6 miles View


Primary Route
Non Primary Route
Former Motorway
Defunct Route
E Road
Future Motorway
Future Primary
Future Non Primary
Historical Route
Tourist Route
Roman Road
Unbuilt Motorway
Unbuilt Primary
Unbuilt Non Primary
National Cycle Network
Cycle Route
Eurovelo Cycle Route


Main Article: Monmouthshire Turnpikes


Main Article: Junctions in Monmouthshire

Bridges, Tunnels, and other Crossings

Main Article: Crossings in Monmouthshire

A40 • A48 • A48(M) • A437 (Gloucester - Newport) • A449 • A455 (Newport) • A465 • A466 • A467 • A468 • A469 • A471 • A472 • A4042 • A4043 • A4044 (Crumlin - Brynmawr) • A4046 • A4047 • A4047 (Ebbw Vale) • A4048 • A4049 • A4050 (Rhymney) • A4051 • A4052 (Newport) • A4072 (Newport) • A4125 (Little Mill - Abergavenny) • A4136 • A4143 • A4232 • A4281 • A4810 • B4004 (Newport) • B4223 (Monmouth - Huntley) • B4232 (Monmouth - Kings Thorn) • B4233 • B4234 (Raglan - Llanvihangel) • B4235 • B4236 • B4237 • B4237 (Maindee - Docks) • B4238 • B4239 • B4239 (Newport) • B4240 • B4241 • B4242 (Newport) • B4243 (Rogerstone) • B4244 • B4245 • B4245 (Little Mill - Abergavenny) • B4246 • B4247 (Monmouthshire) • B4248 • B4249 • B4250 • B4251 • B4252 • B4253 (Monmouthshire) • B4254 • B4256 • B4257 • B4269 • B4288 (Monmouthshire) • B4293 • B4347 • B4423 (Monmouthshire) • B4458 (Monmouth) • B4471 • B4472 • B4477 (Monmouthshire) • B4478 • B4487 • B4490 • B4511 • B4521 • B4560 • B4562 • B4591 • B4596 • B4598 • Cwmcarn Forest Drive • E30 • E105 (London - Fishguard) • M4 • M48 • NCN4 • T10 (Britain) • T17 (Britain) • T76 (Britain) • T77 (Britain) • T78 (Britain) • T103 (Britain)
Abergavenny • Cardiff • Chepstow • Cwmbran • Ebbw Vale • Monmouth • Newport • Pontypool • Raglan
Related Pictures
View gallery (11)
A48 west of Caerwent - Coppermine - 2369.jpgLevel crossing, Rhiwderin (C) Jaggery - Geograph - 1780922.jpgLevel crossing on a hairpin bend, Risca (C) Jaggery - Geograph - 1759011.jpgMonmouthshire Flag.pngBrynglas tunnels on the M4 - Geograph - 1559769.jpg
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