View source for A40 road

{{Short description|Road in Great Britain, connecting London to Wales}}
{{for multi|the A40 in London|A40 road (London)|other uses|A40 (disambiguation)}}
{{Use dmy dates|date=November 2022}}
{{Use British English|date=February 2013}}
{{Infobox road
| country = GBR
| maint = [[National Highways]], [[English local authorities]], [[South Wales Trunk Road Agent]] and [[North and Mid Wales Trunk Road Agent|North & Mid Wales Trunk Road Agent]]
| type = A
| route = 40
| map = [[File:A40 road map.png|200px]]
| map_custom = yes
| image = Holborn Viaduct December 2005.jpg
| image_notes = [[Holborn Viaduct]] carries the A40
| length_mi = 261.2
| length_ref = <ref name="Seg1"/><ref name="Seg2"/><ref name="Seg3"/>
| direction_a = East
| direction_b = West
| terminus_a = {{Jct|country=GBR|A|1|A|1121}} in [[City of London]]
| destinations = [[London]], [[Beaconsfield]], [[High Wycombe]], [[Oxford]], [[Cheltenham]], [[Gloucester]], [[Ross-on-Wye]], [[Monmouth]], [[Abergavenny]], [[Brecon]], [[Llandovery]], [[Llandeilo]], [[Carmarthen]], [[Haverfordwest]], [[Fishguard]]
| terminus_b = [[Goodwick]] ([[Fishguard]])
| junction = <div>''see also: [[A40 road (London)]]''
{{jct|country=GBR|A|5}} in [[Greater London]]<br>
{{jct|country=GBR|M|40|dab1=Great Britain}} in Greater London<br>
{{jct|country=GBR|A|34|A|44}} near [[Oxford]]<br>
{{jct|country=GBR|M|5|dab1=Great Britain}} near [[Cheltenham]]<br>
{{jct|country=GBR|A|38}} in [[Gloucester]]<br>
{{jct|country=GBR|A|48}} near [[Gloucester]]<br>
{{jct|country=GBR|A|49}} at [[Bridstow]]
</div>
| counties = '''England''':<br>[[Greater London]], [[Buckinghamshire]], [[Oxfordshire]], [[Gloucestershire]], [[Herefordshire]]<br>'''Wales''':<br>[[Monmouthshire]], [[Powys]], [[Carmarthenshire]], [[Pembrokeshire]]
| e-road = {{jct|country=EUR|E|30}}
| previous_type = A
| previous_route = 39
| next_type = A
| next_route = 41
}}
The '''A40''' is a [[road]] which runs between [[London]] and [[Goodwick]] ([[Fishguard]]), in [[Wales]]. It is approximately {{convert|260|mi}} long. The eastern section from [[Denham, Buckinghamshire]] to [[Wheatley, Oxfordshire]] is better served by the [[M40 motorway|M40]] and its former function of linking London with Cheltenham and Gloucester has been taken by the M4, A419 and A417 via Swindon.

In 1937, together with the [[A48 road]], it formed parts of the London–Fishguard [[trunk road]], as well as a part of the Newport–Shrewsbury trunk road. Much of the A40's length within England has been superseded by motorways, such as the M40, and has lost its trunk road status, though it retains the status west of Gloucester and its entirety within Wales.

==History==
===18th century===

====Beaconsfield and Stokenchurch Turnpike====
{{anchor|Beaconsfield and Stokenchurch Road Act 1735|Beaconsfield and Stokenchurch Road Act 1759|Beaconsfield and Stokenchurch Road Act 1775|Beaconsfield and Stokenchurch Road Act 1794|Beaconsfield and Stokenchurch Road Act 1823}}

The road between Beaconsfield and Stokenchurch, that later became part of the A40, was put under the management of a [[turnpike trust]] by the '''{{visible anchor|Beaconsfield and Stokenchurch Road Act 1718}}''' ([[5 Geo. 1]]. c. ''2'' {{small|Pr.}})

===20th century===
The A40's 1923 route was from the [[City of London]] to Fishguard. The road still begins and ends in the same places, but a number of changes have been made to its route.{{cn|date=September 2025}}

On 1 April 1937, parts of the road and the [[A48 road]] was classed to form the London–Fishguard [[trunk road]]. Part of the road was also made part of the Newport–Shrewsbury trunk road.<ref name="Act 193622">{{cite web |title=Trunk Roads Act 1936 |url=http://www.legislation.gov.uk/ukpga/1936/5/pdfs/ukpga_19360005_en.pdf |accessdate=2025-09-09 |publisher=[[Legislation.gov.uk]]}}</ref>''<ref name="Watson2">{{cite web |title=Trunk Roads Act 1936 and 1946 |url=http://www.watsonlv.net/pdf/trunk_roads.pdf |accessdate=2025-09-09 |publisher=Leslie V Watson}}</ref>''

The first change dates from 1935, between [[Ross-on-Wye]] and [[Abergavenny]].  The original route of the A40 was via [[Skenfrith]], avoiding Monmouth; this road was renumbered the B4521. The A40 was rerouted via [[Raglan, Monmouthshire|Raglan]]; between Ross and Raglan it replaced part of the A48, between Raglan and Llanvihangel-nigh-Usk it replaced the B4234, and between Llanvihangel and Abergavenny it replaced part of the A471. 

Subsequently, the A40 was rerouted within west London.  Western Avenue dates from the 1930s, but was originally opened as the A403.  After the Second World War, the A40 was rerouted along part of the A219 (west of Notting Hill) and Western Avenue. The old route (via Acton, Ealing, Southall, Hayes, Hillingdon and Uxbridge) was renumbered the A4020.

Initially, the A40 went through the centre of Oxford, via [[Headington]], [[Magdalen Bridge]], the [[High Street, Oxford|High Street]], [[Carfax, Oxford|Carfax]] and [[Botley, Oxfordshire|Botley]], and over the [[Swinford Toll Bridge]] to [[Eynsham]].  It was rerouted in the 1930s to follow the first section of the [[Oxford Ring Road]] to the north of the city, and then followed a direct line to [[Bypass (road)|bypass]] Eynsham.  The old route became part of the [[A420 road|A420]] to Botley, and the section between Botley and Eynsham was renumbered the A4141,<ref>{{cite web|url=http://www.visionofbritain.org.uk/maps/series?xCenter=3249330.6417157&yCenter=2830691.8632341&scale=63360&viewScale=181417.4208&mapLayer=europe&subLayer=new_pop&title=British%20War%20Office%20GSGS%204127%2C%20Ordnance%20Survey%20Popular%20and%20New%20Popular%20Editions&download=true|title=New Popular Edition, Sheet 158|publisher=[[Ordnance Survey of Great Britain]]|access-date=25 January 2020|archive-date=25 August 2020|archive-url=https://web.archive.org/web/20200825144027/https://www.visionofbritain.org.uk/maps/series?xCenter=3249330.6417157&yCenter=2830691.8632341&scale=63360&viewScale=181417.4208&mapLayer=europe&subLayer=new_pop&title=British+War+Office+GSGS+4127%2C+Ordnance+Survey+Popular+and+New+Popular+Editions&download=true|url-status=live}}</ref> renumbered again in the 1960s to the B4044.

From the 1960s to 1990s a number of bypasses were built to divert the A40 around towns on the route, including Gloucester (1968), Monmouth (1964), Brecon (1980), Carmarthen (1984), St. Clears (1984), Whitland (1994).

In the mid-1980s a new dual carriageway was built for the A40 between Raglan and Abergavenny, and the 1935 route was renumbered the B4598.

==Route==
===Central London – Denham===
{{main|A40 road in London}}
In central London it is [[Holborn|High Holborn]] and then [[Oxford Street]]. At [[Marble Arch]] it joins the [[A5 road (Great Britain)|A5]] [[Edgware Road]] as far as the Marylebone Flyover to become [[Westway (London)|Westway]] (classified A40(M) as an elevated motorway) then meets [[Western Avenue, London|Western Avenue]]. For the greater part, this section is six lanes, otherwise four lanes. With two exceptions, Western Avenue forms a grade-separated motorway standard dual-carriageway between Paddington and the [[M40 motorway]]. The two [[at-grade intersection]]s are Gypsy Corner and Savoy Circus; both of which are [[traffic light]] controlled. At [[Denham Roundabout]], the six lane Western Avenue flows into the [[M40 motorway|M40]].

=== Denham – Oxford ===
The A40 branches off the Denham roundabout to run as a dual carriageway. After the junction with the [[A413 road|A413]], the A40 follows the same route as the M40 as a single carriageway, passing through [[Beaconsfield]] and [[High Wycombe]]. Beyond [[Stokenchurch]] the road is much quieter; when meeting the B4009 and A329 those roads have priority. Approaching [[Oxford]], the A40 becomes a busy dual carriageway, carrying traffic from the M40 to Oxford and beyond. The road forms the northern section of the [[Oxford Ring Road]], crossing the [[A44 road|A44]] and the [[A34 road|A34]]. In Oxford, it passes the Thornhill Park and Ride, where the OxfordTube, The Airline to Heathrow & Gatwick, & Oxford Park and Ride buses stop.

===Oxford – Cheltenham (M5)===
The A40 passes under the [[A34 road (England)|A34]], reverting to single carriageway for {{convert|10|mi}} until the dual carriageway just east of [[Witney]] with a grade-separated junction. The dual carriageway finishes at a roundabout. For the rest of [[Oxfordshire]] and [[Gloucestershire]] until [[Cheltenham]], other than for a few short stretches, the road is single carriageway. A height of {{convert|820|ft}} above sea level is located {{convert|3|mi}} west of the A429 junction. Before [[Andoversford]] the [[A436 road (Great Britain)|A436]] breaks off to the west to try to take traffic away from descending into the centre of Cheltenham itself. The road travels through Cheltenham town centre along at least two parallel routes (neither is part of a one-way system: Sandford Road and Montpellier Terrace make up one part, Thirlestaine Road and Suffolk Road the other). Becoming a dual carriageway, it passes [[GCHQ]] in Cheltenham and the [[roundabout interchange#Three-level stacked roundabout|three-level stacked roundabout interchange]] with the [[M5 motorway]]. In February 2015, the Witney Oxford Transport Group proposed the reopening of [[Yarnton railway station]] as an alternative to improvements to the A40 road proposed by [[Oxfordshire County Council]].<ref>{{cite news |last=Elvery |first=Martin |url=http://www.witneygazette.co.uk/news/11771480.Campaigners_want_new_railway_station_at_Yarnton_to_ease_A40_congestion/?ref=mr |title=Campaigners want new railway station at Yarnton to ease A40 congestion in West Oxfordshire |work=Witney Gazette |date=2015-02-05 |access-date=2015-02-12 |archive-date=23 September 2016 |archive-url=https://web.archive.org/web/20160923020043/http://www.witneygazette.co.uk/news/11771480.Campaigners_want_new_railway_station_at_Yarnton_to_ease_A40_congestion/?ref=mr |url-status=live }}</ref><ref>{{Cite web |url=http://www.oxfordshireguardian.co.uk/bid-to-reopen-train-track-ahead-of-key-rail-summit/ |title=Bid to reopen Witney train track ahead of key rail summit |access-date=21 September 2016 |archive-url=https://web.archive.org/web/20160923041805/http://www.oxfordshireguardian.co.uk/bid-to-reopen-train-track-ahead-of-key-rail-summit/ |archive-date=23 September 2016 |url-status=dead }}</ref>

===Cheltenham (M5) – Abergavenny===
The A40 is the [[Gloucester]] bypass, most of which is dual carriageway. The junction with the [[A48 road|A48]] to [[Chepstow]] is at Highnam. For the remainder of Gloucestershire, and a part of [[Herefordshire]], the road is single carriageway until [[Ross-on-Wye]]. There it connects with the [[M50 motorway (Great Britain)|M50 motorway]], and forms part of the high quality dual carriageway between [[South Wales]] and the [[English Midlands]]. From Ross-on-Wye to [[Monmouth]] the road follows the [[Wye Valley]], an [[Area of Outstanding Natural Beauty]], crossing the [[Wales–England border]] {{cvt|1|mi|sing=on}} east of Monmouth. Just west of Monmouth are twin tunnels; these are the only tunnels on the A40. Near [[Raglan, Monmouthshire|Raglan]], the A40 has a grade separated junction with the [[A449 road|A449]]. The A40 continues as a dual carriageway to [[Abergavenny]].

====Abergavenny – M50 junctions====
{{RJL|date=December 2021}}
{| border=1 cellpadding=2 style="margin-left:1em; margin-bottom: 1em; c border-collapse: collapse; " class="wikitable"
|- align="center" bgcolor="#00703C" style="color: #ffd200;"
| colspan="3" | '''A40 (T)''' 
|- align="center"
| '''Eastbound exits'''
| '''Junction'''
| '''Westbound exits'''
|- align="center"
| [[Midlands|The Midlands]] [[Worcester, England|Worcester]] ('''[[M50 motorway (Great Britain)|M50]]''') <br> [[Ross-on-Wye]]
| ''Roundabout''
| Ross-on-Wye <br> The MIDLANDS Worcester ('''M50''')
|-align="center"
| [[Hereford]] '''[[A49 road (England)|A49]]''' <br> Ross-on-Wye '''B4260'''
| Wilton Roundabout
| Ross-on-Wye '''B4260''' <br> Hereford '''A49'''
|-align="center"
| [[Goodrich, Herefordshire|Goodrich]]
| Goodrich Junction
| Goodrich
|-align="center"
| Hereford '''[[A4137 road|A4137]]''' <br> Goodrich '''B4229'''
| Old Ross Road Junction
| Hereford '''A4137''' <br> Goodrich '''B4229'''
|-align="center"
| [[Whitchurch, Herefordshire|Whitchurch]], [[Symond's Yat]] (West)
| Whitchurch Junction
| Whitchurch, Symond's Yat (West)
|- align="center"
| {{no2}}Exit only <br> Whitchurch
| Whitchurch South Junction
| {{no2}}No exit or access
|- align="center"
| {{no2}} No exit or access
| Oak House Junction
| Crocker's Ash, Doward
|-align="center"
| [[Monmouth]] '''[[A466]]''' <br> [[Chepstow]] ('''A466'''), [[Forest of Dean]] ('''A4136''') '''A40'''
| Old Dixon Roundabout
| Monmouth '''A466'''
|-align="center"
| Monmouth '''A466'''
| Wye Bridge Junction
| Chepstow ('''A466'''), Forest of Dean ('''A4136''')
|-align="center"
| Monmouth, [[Trelleck]] '''B4293'''
| Monnow Bridge Junction
| Monmouth, [[Trelleck]] '''B4293'''
|-align="center"
| {{no2}}No access or exit
| Mitchel Troy Junction
| {{no2}}Access only
|-align="center"
| [[Newport, Wales|Newport]] '''[[A449]]'''
| Raglan Interchange
| Newport, [[Cardiff]] ('''[[M4 motorway|M4]]''') '''A449'''
|-align="center"
| [[Abergavenny]] ('''A40'''), [[Raglan, Monmouthshire|Raglan]], [[Mitchel Troy]]
| Raglan Junction
| Raglan <br> Mitchel Troy, [[Dingestow]]
|-align="center"
| [[Clytha]] <br> Raglan <br> [[Gwehelog]]
| Raglan Roundabout
| Raglan <br> Gwehelog <br> Clytha
|- align="center"
| [[Hereford]] '''[[A465]]''' <br> [[Usk]], Clytha '''B4598'''
| rowspan="2"| Ysbytty Fields Roundabout
| {{no2}}No access or exit
|- align="center"
| Newport '''[[A4042]]''' <br> [[Merthyr Tydfil]] '''A465''' 
| Newport '''A4042'''<br> Merthyr Tydfil '''A465''' <br> Hereford '''A465'''
|}

===Abergavenny – Carmarthen===
At Abergavenny is the A40 junction with the Heads of the Valleys road, ([[A465 road|A465]]) and the A4042. Now the A465 becomes the primary route between the Midlands to the [[South Wales Valleys]] and Swansea; there is a dual-carriageway route to [[Carmarthen]] via the A465, M4 and A48.

The A40 becomes single carriageway and continues through Abergavenny, following the north side of the [[River Usk|Usk valley]] through the eastern part of the [[Brecon Beacons National Park]] until [[Brecon]]. At [[Bwlch]] between Abergavenny and Brecon, the A40 is {{convert|660|ft}} above sea level. The A40 is dualed for over {{convert|1.5|mi}} as it approaches a junction east of Brecon with the [[A470 road|A470]] north, which is the main north–south road through mid-Wales. Continuing as a dual carriageway, the A40 and A470 concurrent bypass Brecon to the south, crossing the River Usk here. At the western end of the bypass is a further junction with the A470 south.  Beyond this point the A40 continues as a single carriageway, now south of the River Usk, and roughly follows the northern edge of the Brecon Beacons National Park. A height of {{convert|820|ft}} above sea level is located less than {{convert|1|mi}} east of [[Trecastle]]. In [[Llandovery]] the road crosses the [[Heart of Wales line|Heart of Wales railway]] and the [[River Tywi]]; the road, railway and river then run parallel until [[Llandeilo]], where the National Park ends and the railway turns south. The A40 continues west along the Tywi valley to Carmarthen where as a dual carriageway it forms the eastern bypass, meeting the terminus of the A48 at Pensarn. Here the A40 returns to being a primary route westwards.

===Carmarthen – Fishguard===
At Carmarthen the A40 crosses the [[River Tywi]] twice with two 90-degree junctions and continues on {{convert|10|mi}} of dual carriageway as far as [[St. Clears]], where the dual carriageway ends at the junction with the [[A477 road|A477]] [[trunk road]]. Now the A40 is a mixture of 2 or 3 lane single-carriageway to [[Haverfordwest]] and [[Fishguard]]. This section of road is controlled by the [[Welsh Government]] (formerly 'Welsh Assembly Government'), which describes it as "one of the lowest standard sections of the Trans European Road Network in the United Kingdom".<ref name="WPCleanerAuto1">{{Cite web |url=http://wales.gov.uk/docs/det/policy/060825A40.pdf |title=Welsh Assembly Government |access-date=1 April 2011 |archive-date=10 April 2012 |archive-url=https://web.archive.org/web/20120410033148/http://wales.gov.uk/docs/det/policy/060825A40.pdf |url-status=live }}</ref>

====St Clears to Haverfordwest dualling====
There were plans in 2002 for a major improvement of the 23-mile stretch between St Clears and Haverfordwest which included upgrading to a dual carriageway; described as an extension of the national motorway network to the West Wales coast by virtue of the route from the [[M4 motorway]] being entirely dual carriageway.<ref>{{cite news| url=http://news.bbc.co.uk/2/hi/uk_news/wales/1885220.stm| title=Dual carriageway for west Wales| publisher=BBC News| date=2002-03-21| access-date=31 March 2011| archive-date=6 December 2008| archive-url=https://web.archive.org/web/20081206105917/http://news.bbc.co.uk/2/hi/uk_news/wales/1885220.stm| url-status=live}}</ref> The £60&nbsp;million scheme was subject to a European Environmental Assessment.  Within a couple of years, the project appeared to be dying a very quiet death, causing local newspapers to report it being an election stunt for the two marginal constituencies that would best benefit from the improvements.  The following Welsh elections saw both constituencies change the party of majority.  The political party at the centre of the row instead directed the project deferment to damning environmental statements by Friends of the Earth Cymru.<ref>{{Cite web |url=http://www.foe.co.uk/cymru/english/press_releases/a40_safety_challenged.html |title=A40 dual carriageway safety claim challenged |access-date=31 March 2011 |archive-date=19 August 2010 |archive-url=https://web.archive.org/web/20100819123653/http://www.foe.co.uk/cymru/english/press_releases/a40_safety_challenged.html |url-status=live }}</ref><ref>{{Cite web |url=http://www.foe.co.uk/resource/briefings/proposed_a40_dualling.pdf |title=FOE Briefing |access-date=31 March 2011 |archive-date=20 March 2012 |archive-url=https://web.archive.org/web/20120320085515/http://www.foe.co.uk/resource/briefings/proposed_a40_dualling.pdf |url-status=live }}</ref> The scheme was officially scrapped in 2008 after a Welsh Assembly committee decided to abandon the proposals.  Instead, it recommended upgrades to the existing route including bypasses around [[Robeston Wathen]] and [[Llanddewi Velfrey]] using a three-lane option.  This was welcomed by the [[Friends of the Earth]], saying "The dual carriageway on the A40 would increase traffic levels, increase the emission of greenhouse gases, it would be harmful for the environment, it would be hugely expensive. That money would be better spent on improving public transport, on health, on education, there's no need for it. We think the assembly committee has come to the right decision".<ref>{{cite news|url=http://news.bbc.co.uk/2/hi/uk_news/wales/wales_politics/7765939.stm|title=A40 dual carriageway plan blocked|publisher=BBC News|date=2008-12-04|access-date=1 April 2011|archive-date=5 December 2008|archive-url=https://web.archive.org/web/20081205195820/http://news.bbc.co.uk/2/hi/uk_news/wales/wales_politics/7765939.stm|url-status=live}}</ref>

====Whitland Bypass====
The last improvement to the A40 on this section prior to the Welsh Assembly Government having the devolved responsibility for this road was a {{convert|4.1|km}} £8&nbsp;million bypass around [[Whitland]].  Constructed in 1994, the road started east of Black Bridge on the original A40, then running north of the town before to a new roundabout just west of Llain Cottage.  The Secretary of State for Wales was asked a written question by [[Rhodri Morgan]] about adding a second carriageway to the Whitland bypass scheme, to which [[John Redwood]] replied "There are no proposals to add a second carriageway to the Whitland bypass. The design capacity of a single carriageway two-lane highway is more than adequate to cater with the anticipated traffic flows for the foreseeable future."<ref>{{Cite web |url=https://api.parliament.uk/historic-hansard/written-answers/1995/feb/03/whitland-bypass |title=Hansard |access-date=1 April 2011 |archive-date=20 October 2012 |archive-url=https://web.archive.org/web/20121020183204/http://hansard.millbanksystems.com/written_answers/1995/feb/03/whitland-bypass |work=[[Hansard|Parliamentary Debates (Hansard)]] |date=3 February 1995 |url-status=live }}</ref>

====Llanddewi Velfrey Bypass====
A new bypass has been granted approval by the Welsh Assembly Government at [[Llanddewi Velfrey]] in [[Pembrokeshire]].  The scheme would improve the A40 between [[Llanddewi Velfrey]] and [[Penblewin]], to the west of St Clears and meet the aim of the targeted investment in infrastructure along the east–west road corridor in south Wales.<ref>[http://wales.gov.uk/topics/transport/roads/schemes/ewsouth/a40llanddewi Welsh Assembly Government]</ref> From the east, it is proposed that a roundabout would be created just north of Glenfield Farm, where the straight section from St Clears ends at Bethel Chapel, and then take a new route north-west of the town of Llanddewi Velfrey, south-west over Pentroydin Fawr and Penttroydin Fech farms with cattle underpasses, a new underpass beneath the existing Llanddewi Velfrey to [[Llanfallteg]] road, before going over the original A40 at [[Ffynnon Wood]].  To the west of Ffynnon Wood, the road would then cross back over the original A40 to the east of [[Henllan Lodge]] in a way to maintain the tree lined avenue to Henllan, then run parallel to the A40 on the north side of the existing A40 to a new roundabout at Penblewin and the junction with the [[A478 road|A478]].<ref>{{Cite web |url=http://wales.gov.uk/docs/det/policy/060825A40routemap.pdf |title=Llanddewi Velfrey Bypass Route (Welsh Assembly Government |access-date=1 April 2011 |archive-date=10 April 2012 |archive-url=https://web.archive.org/web/20120410033148/http://wales.gov.uk/docs/det/policy/060825A40routemap.pdf |url-status=live }}</ref>

This was originally known as the Blue and Purple routes during the Consultation in 2006<ref>{{Cite web |url=http://wales.gov.uk/docs/det/policy/060825A40.pdf |title=A40 Llanddewi Velfrey to Penblewin Public Consultation |access-date=1 April 2011 |archive-date=10 April 2012 |archive-url=https://web.archive.org/web/20120410033148/http://wales.gov.uk/docs/det/policy/060825A40.pdf |url-status=live }}</ref> for which 75% preferred the blue route, and only 20% preferred the red route.  54% felt the section from Ffynnon Wood and Penblewin Roundabout needed improvement, with both orange and purple routes preferred by 42% of the respondents. [[Dwr Cymru|Welsh Water/Dwr Cymru]] expressed concerns with the red route affecting water mains and sewers, and Henllanfallteg Community Council felt the red route would not improve the quality of life in Llanddewi Velfrey. [[Pembrokeshire County Council]] expressed concerns that the route planned was a single carriageway, and that within seven years, a dual carriageway would be required.

====Robeston Wathen Bypass====
A new bypass has been constructed between Penblewin and Slebech Park making the road straighter and with a '2+1' road layout to help improve overtaking opportunities.<ref>{{Cite web |url=http://wales.gov.uk/newsroom/transport/2011/110316penblewin/?lang=en |title=Welsh Assembly Government: Penblewin Improvements |access-date=1 April 2011 |archive-date=30 March 2012 |archive-url=https://web.archive.org/web/20120330110008/http://wales.gov.uk/newsroom/transport/2011/110316penblewin/?lang=en |url-status=dead }} </ref>

Starting to the west of Toch Lane (approx. {{convert|2|km}} east of [[Slebech]]), the route travels eastwards for {{convert|4.6|km}}, passing {{convert|200|m}} south of [[Robeston Wathen]], and ending {{convert|0.5|km}} east of the village, just west of Flimstone Lane.

Construction started on the route in February 2009, with the works completed and the new road opening 1 March 2011.  The road was built by [[Costain Group|Costain]].  The scheme was nearly £14&nbsp;million over the initial budget of £27.6&nbsp;million, eventually costing £41.4&nbsp;million.  The Welsh Assembly Government explains this increase as being the result of inflation and land costs, saying the original budget did not include either, as well as additional statutory procedures, additional works following some design standards, and the increase in VAT.<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-wales-12756563|title=Over-budget Penblewin to Slebech Park bypass opens|date=2011-03-16|publisher=BBC News|access-date=20 June 2018|archive-date=1 January 2018|archive-url=https://web.archive.org/web/20180101070050/http://www.bbc.co.uk/news/uk-wales-12756563|url-status=live}}</ref>

====The Kell====
The Kell is located on a section of the A40 that forms a north–south corridor between [[Fishguard]], {{convert|17|km}} to the north and [[Haverfordwest]], {{convert|7.5|km}} to the south, close to [[Treffgarne]] and [[Spittal, Pembrokeshire|Spittal]]. The improvement saw about {{convert|0.48|km}} of new trunk road commencing at a point on the trunk road approximately 622 metres south of the centreline of the junction of the A40 trunk road with the C3059 road to Spittal and extending in a generally northerly direction to a point approximately 112 metres south of the junction of the trunk road with the C3059 road to Spittal.<ref>{{Cite web |url=http://www.legislation.gov.uk/wsi/2009/3192/pdfs/wsi_20093192_mi.pdf |title=Statutory Instrument 3192 (2009) |access-date=1 April 2011 |archive-date=17 December 2010 |archive-url=https://web.archive.org/web/20101217193331/http://www.legislation.gov.uk/wsi/2009/3192/pdfs/wsi_20093192_mi.pdf |url-status=live }}</ref> This resulted in the road being rerouted through pasture to the east of the original road, taking a right hand bend about {{convert|160|m}} south of The Old Mill, taking a 5.5% gradient, and rejoining the original road {{convert|210|m}} north of The Kell.  The original road has subsequently been converted to an access road for The Old Mill, Beavers Lodge and The Kell, accessing the new road at The Old Mill.

====Fishguard Bypass====
The Fishguard Bypass was planned to provide a more direct route with greater capacity to the Port of Fishguard at Goodwick avoiding the town centre of Fishguard. It was constructed during the late 1990s and opened in 2000. It takes the form of a three-lane carriageway on an approx. 10% gradient around the western edge of Fishguard. It runs from its highest point at Rafael roundabout 1&nbsp;km south of Fishguard town in a generally northerly direction to its lowest point at Windy Hall roundabout where it rejoins the old A40 route at Gasworks Hill. The bypass is concurrent with a section of the A487 trunk road with the A40 dominant.<ref>{{Cite web |url=https://www.geograph.org.uk/photo/331547 |title=Fishguard Bypass Roundabout |access-date=9 December 2017 |archive-date=9 December 2018 |archive-url=https://web.archive.org/web/20181209082114/http://www.geograph.org.uk/photo/331547 |url-status=live }}</ref><ref>{{Cite web |url=https://www.geograph.org.uk/photo/2021037 |title=Rafael Roundabout |access-date=9 December 2017 |archive-date=3 October 2018 |archive-url=https://web.archive.org/web/20181003102621/http://www.geograph.org.uk/photo/2021037 |url-status=live }}</ref>

==Junction list==
===A40===
{{GBRinttop|length_ref=<ref name="Seg1">{{cite web|url=https://www.google.com/maps/dir/51.891681,-2.1422869/51.6552833,-0.8774944/51.5184726,-0.1704361/51.5135123,-0.1578199/51.5155622,-0.1400304/51.5177015,-0.0973343/@51.8905232,-2.1427528,17z/data=!4m4!4m3!2m1!1b1!3e0?hl=en&entry=ttu|title=A40, Cheltenham GL51 6SL, UK to Stokenchurch, United Kingdom to 27 Praed St, London W2 1NJ, UK to Marble Arch Station (Stop P), London W1K 7JA, United Kingdom to 1 – 4 Argyll St, London W1F 7LD, UK to 140 London Wall, Barbican, London EC2Y 5DN, UK|work=[[Google Maps]]|publisher=[[Alphabet Inc.]]|access-date=28 February 2024}}</ref>
<ref name="Seg2">{{cite web|url=https://www.google.com/maps/dir/51.8915849,-2.1422373/51.8851637,-2.4695686/51.8185794,-3.0138838/51.9042973,-3.9624487/@51.899816,-3.9656048,15z/data=!4m4!4m3!2m1!1b1!3e0?hl=en&entry=ttu|title=A40, Cheltenham GL51 6SL, UK to A40, Longhope GL17 0LP, UK to 8-16 A40, Abergavenny, UK to A40, Llandeilo, UK|work=[[Google Maps]]|publisher=[[Alphabet Inc.]]|access-date=28 May 2024}}</ref>
<ref name="Seg3">{{cite web|url=https://www.google.com/maps/dir/51.9042973,-3.9624487/52.003192,-4.9933246/@52.0026013,-4.9947352,16z/data=!4m4!4m3!2m1!1b1!3e0!5m1!1e4?hl=en&entry=ttu|title=A40, Llandeilo, UK to The Parrog, Goodwick SA64 0DE, UK|work=[[Google Maps]]|publisher=[[Alphabet Inc.]]|access-date=30 May 2024}}</ref>
}}
{{GBRint
|county_special=[[Greater London]]
|cspan=24
|location=City of London
|mile=0.0
|road={{Jct|country=GBR|road|[[Goswell Road]] ([[A1 road (Great Britain)|A1]] north) / [[London Wall]] ([[A1211 road|A1121]] east)|location1=[[Angel, London|Angel]]|city2=Islington}}
|notes=Eastern terminus; southern terminus of A1; western terminus of A1211
}}
{{GBRint
|location_special=[[City of London]]-[[London Borough of Camden|Camden]] boundary
|mile=0.6
|road=New Fetter Lane ([[A4 road (England)|A4]] west) / Hatton Garden (B521) / Charterhouse Street
|notes=Eastern terminus of A4
}}
{{GBRint
|type=concur
|location_special=[[London Borough of Camden|Camden]]
|lspan=2
|mile=1.2
|road=[[Theobalds Road]] ([[A401 road|A401]] east)
|notes=Eastern terminus of A401 concurrency
}}
{{GBRint
|type=incomplete
|mile=1.3
|road=[[A4200 road|Kingsway / Southampton Row (A4200)]]
|notes=No access from A40 east to A4200, from A4200 south to A40, or from A4200 north to A40 east
}}
{{GBRint
|type=concur
|location_special=[[London Borough of Camden|Camden]]-[[Westminster]] boundary
|mile=1.6
|mile2=1.7
|road={{Jct|country=GBR|A|400|road|Shaftesbury Avenue ([[A401 road|A401]] west)|A|501|name1=Bloomsbury Street / Tottenham Court Road / Charging Cross Road|city1=Camden Town|location2=[[West End of London|West End]]|city3=Westminster}}
|notes=West End and Westminster signed westbound only; western terminus of A401 concurrency
}}
{{GBRint
|type=incomplete
|location=Westminster
|lspan=8
|mile=2.2
|road=Regent Street ([[A4201 road|A4201]])
|notes=No right-hand turns
}}
{{GBRint
|mile=2.7
|road=Orchard Street ([[A41 road|A41]] west) / North Audley Street
|notes=Eastern terminus of A41
}}
{{GBRint
|mile=2.8
|road=Portman Street ([[A4380 road|A4380]] north) / Park Street
|notes=Southern terminus of A4380
}}
{{GBRint
|type=concur
|mile=3.0
|road={{Jct|country=GBR|road|[[London Inner Ring Road|Ring Road]] south ([[Park Lane|Park Lane / A4202]] south)|A|402|A|4|A|3|dir2=west|name2=Bayswater Road|to3=yes|city1=Westminster|city2=Notting Hill|city3=Knightsbridge|location4=[[Victoria, London|Victoria]]}}
|notes=Knightsbridge and Victoria signed westbound only; eastern terminus of A5 / Ring Road concurrency; southern terminus of A5; eastern terminus of A402
}}
{{GBRint
|type=incomplete
|mile=3.1
|road=Wigmore Street ([[A5204 road|A5204]] east) / Seymour Street
|notes=No access from A40 to A5204; western terminus of A5204
}}
{{GBRint
|type=incomplete
|mile=3.5
|road=Old Marylebone Road ([[A501 road|A501]] east) / Sussex Gardens ([[A4209 road|A4209]] south-west)
|notes=No access from A40 to A501, from A40 east to A4209, from A501 to A40 west, or from A4209 to A40 east; north-eastern terminus of A4209
}}
{{jctbridge
|type=incomplete
|mile=3.6
|bridge=A40 jumps from concurrency with {{Jct|country=GBR|A|5}} to the [[Westway (London)|Westway]] without any direct connection{{note|Mileage is based on shortest route between this spot and the Westway.}}
}}
{{GBRint
|type=incomplete
|mile=4.7
|road=To [[London Inner Ring Road|Ring Road]] south - [[West End of London|West End]], [[Paddington]]
|notes=[[Interchange (road)|Grade-separated junction]]; eastbound exit and westbound entrance
}}
{{GBRint
|location_special=[[Royal Borough of Kensington and Chelsea|Kensington and Chelsea]]-[[London Borough of Hammersmith and Fulham|Hammersmith and Fulham]] borough boundary
|mile=6.0
|mile2=6.3
|road={{Jct|country=GBR|A|3220|dir1=south|city1=Hammersmith|city2=Shepherd's Bush|city3=Earl's Court|city4=Westminster}}
|notes=Grade-separated junction; Westminster signed eastbound only
}}
{{GBRint
|type=incomplete
|location_special=[[London Borough of Hammersmith and Fulham|Hammersmith and Fulham]]
|mile=6.5
|road={{Jct|country=GBR|A|219|city1=Harlesden|location2=[[White City, London|White City]]}}
|notes=Grade-separated junction; Eastbound exit and westbound entrance
}}
{{GBRint
|location_special=[[London Borough of Ealing|Ealing]]
|lspan=6
|mile=8.1
|mile2=8.3
|road={{Jct|country=GBR|A|4000|B|4492|city1=Harlesden|city2=Willesden|location3=[[Acton, London|Acton]]|city4=Park Royal}}
|notes=
}}
{{GBRint
|type=incomplete
|mile=9.5
|road=[[Park Royal]] (central)
|notes=Grade-separated junction; eastbound exit only
}}
{{GBRint
|mile=9.4
|mile2=10.0
|road={{Jct|country=GBR|A|406|M|1|M|4|A|41|A|1|name1=[[North Circular Road|North Circular]]|city1=Wembley|city2=Ealing}}
|notes=
}}
{{GBRint
|mile=10.9
|mile2=11.5
|road=[[Perivale]]
|notes=Grade-separated junction
}}
{{GBRint
|mile=11.9
|mile2=12.3
|road={{Jct|country=GBR|A|4127|location1=[[Harrow, London|Harrow]]|location2=[[Sudbury, London|Sudbury]]|city3=Greenford}}
|notes=Grade-separated junction
}}
{{GBRint
|mile=13.3
|mile2=13.9
|road={{Jct|country=GBR|A|312|location1=[[Heathrow Airport]]|location2=[[Hayes, Hillingdon|Hayes]]|city3=Southall|city4=Yeading|city5=Northolt|extra=airport}}
|notes=Grade-separated junction; Heathrow, Hayes, Southall and Yeading signed westbound only, Northolt eastbound only
}}
{{GBRint
|location_special=[[London Borough of Hillingdon|Hillingdon]]
|lspan=3
|mile=14.4
|mile2=14.9
|road={{Jct|country=GBR|A|4180|city1=Ruislip|location2=[[Heathrow Airport]]|location3=[[Hayes, Hillingdon|Hayes]]|city4=Southall|city5=Yeading|extra=airport}}
|notes=Grade-separated junction; Ruislip signed westbound only, Heathrow, Hayes, Southall and Yeading eastbound only
}}
{{GBRint
|mile=16.3
|mile2=17.2
|road={{Jct|country=GBR|A|437|B|466|city1=Hillingdon|city2=Ruislip|city3=Ickenham}}
|notes=Grade-separated junction
}}
{{GBRint
|mile=17.5
|mile2=17.9
|road={{Jct|country=GBR|B|467|city1=Uxbridge|city2=Harefield|city3=Ickenham|city4=Ruislip}}
|notes=Grade-separated junction; Ruislip signed eastbound only
}}
{{GBRint
|type=concur
|county=Buckinghamshire
|cspan=9
|location_special=[[Denham, Buckinghamshire|Denham]]
|lspan=3
|mile=18.5
|mile2=19.1
|road={{Jct|country=GBR|M|40|M|25|dir1=north-west|to2=yes|city1=Oxford|city2=Birmingham|city3=Beaconsfield|city4=Watford}}<br>{{Jct|country=GBR|A|4020|dir1=east|name1=Oxford Road|city1=Uxbridge|location2=[[Denham, Buckinghamshire|Denham]]}}<br>{{Jct|country=GBR|A|412|dir1=south|name1=Denham Road|city1=Slough}}
|notes=Birmingham and Beaconsfield signed westbound only, Watford eastbound only; eastern terminus of A412 concurrency; western terminus of A4020
}}
{{GBRint
|type=concur
|mile=19.7
|road={{Jct|country=GBR|A|412|dir1=north|name1=Denham Avenue|city1=Rickmansworth|location2=[[Denham, Buckinghamshire|Higher Denham, Denham Green]]}}
|notes=Western terminus of A412 concurrency
}}
{{GBRint
|mile=20.6
|road={{Jct|country=GBR|A|413|dir1=north|name1=Amersham Road|city1=Amersham|location2=[[Chalfont St Peter|The Chalfonts]]}}
|notes=Southern terminus of A413
}}
{{GBRint
|location=Beaconsfield
|mile=25.5
|road={{Jct|country=GBR|A|355|M|40|M|25|to2=yes|location1=[[Heathrow Airport]]|city2=Slough|city3=Amersham|city4=London|location5=[[High Wycombe|Wycombe]]}}
|notes=London and Wycombe signed westbound only
}}
{{GBRint
|location_special=[[Loudwater, Buckinghamshire|Loudwater]]
|mile=28.7
|road={{Jct|country=GBR|M|40|dir1=east|city1=London|city2=Flackwell Heath}}<br>{{Jct|country=GBR|A|4094|dir1=south|city1=Maidenhead|location2=[[Bourne End, Buckinghamshire|Bourne End]]|city3=Wooburn Green}}
|notes=Flackwell Heath signed westbound only; M4 junction 3; northern terminus of A4094
}}
{{GBRint
|location=High Wycombe
|lspan=2
|mile=31.7
|road={{Jct|country=GBR|A|404|M|4|M|40|to2=yes|city1=Maidenhead|location2=[[Marlow, Buckinghamshire|Marlow]]|city3=Amersham}}
|notes=
}}
{{GBRint
|mile=32.1
|road={{Jct|country=GBR|A|4128|dir1=north|name1=Arch Way|city1=Great Missenden}}
|notes=Southern terminus of A4128
}}
{{GBRint
|type=concur
|location_special=[[High Wycombe]]-[[West Wycombe]] boundary
|mile=33.5
|road={{Jct|country=GBR|A|4010|M|40|A|404|dir1=south|name1=Chapel Lane|to2=yes|location1=[[Marlow, Buckinghamshire|Marlow]]}}
|notes=Information signed eastbound only; eastern terminus of A4010 concurrency
}}
{{GBRint
|type=concur
|location=West Wycombe
|mile=34.1
|road={{Jct|country=GBR|A|4010|dir1=north|name1=Bradenham Road|city1=Aylesbury|city2=Princes Risborough}}
|notes=Western terminus of A4010 concurrency
}}
{{GBRint
|type=concur
|county=Oxfordshire
|cspan=12
|location_special=[[Great Haseley]]-[[Great Milton]]-[[Tiddington-with-Albury]] boundary
|mile=47.6
|road={{Jct|country=GBR|A|329|M|40|name1=Rycote Lane|to2=yes|dir2=south|city1=London|location2=[[High Wycombe|Wycombe]]|location3=[[Wallingford, Oxfordshire|Wallingford]]|city4=Thame|city5=Stadhampton|location6=[[Moreton, South Oxfordshire|Moreton]]}}
|notes=Brief concurrency
}}
{{GBRint
|location_special=[[Great Milton]]-[[Tiddington-with-Albury]] boundary
|lspan=2
|mile=49.1
|road={{Jct|country=GBR|A|418|dir1=north-east|name1=Oxford Road|city1=Aylesbury|location2=[[Tiddington, Oxfordshire|Tiddington]]}}
|notes=Tiddington signed eastbound only; south-western terminus of A418
}}
{{GBRint
|mile=49.7
|mile2=50.3
|road={{Jct|country=GBR|M|40|city1=London|city2=High Wycombe|city3=Birmingham|city4=Banbury}}
|notes=M40 junctions 8-8A
}}
{{GBRint
|type=incomplete
|location_special=[[Wheatley, Oxfordshire|Wheatley]]
|mile=51.9
|road=[[Wheatley, Oxfordshire|Wheatley]], [[Holton, Oxfordshire|Holton]], [[Waterperry]]
|notes=Grade-separated junction; no westbound exit
}}
{{GBRint
|location=Headington
|mile=54.6
|road={{Jct|country=GBR|A|4142|A|420|road|Bayswater Road|dir1=south|dir2=west|name1=[[Oxford Ring Road|Ring Road]]|name2=London Road|location1=[[Oxford|City centre]]|location2=[[Cowley, Oxfordshire|Cowley]]|city3=Headington|location4=[[Barton, Oxfordshire|Barton]]}}
|notes=Northern terminus of A4142; eastern terminus of A420
}}
{{GBRint
|location_special=[[Marston, Oxford|Marston]]
|mile=56.3
|road=[[Marston, Oxford|Marston]], [[Elsfield]]
|notes=Grade-separated junction
}}
{{GBRint
|location=Cutteslowe
|lspan=2
|mile=58.3
|road={{Jct|country=GBR|A|4165|name1=Banbury Road|location1=[[Summertown, Oxford|Summertown]]|city2=Kidlington|location3=[[Gosford, Oxfordshire|Gosford]]}}
|notes=
}}
{{GBRint
|mile=58.7
|road={{Jct|country=GBR|A|44|road|Woodstock Road ([[A4144 road|A4144]] south) / Five Mile Drive|A|34|M|40|A|420|dir1=west|to3=yes|name1=[[Oxford Ring Road|Ring Road]]|city1=Midlands|city2=Evesham|location3=[[Newbury, Berkshire|Newbury]]|location4=[[Oxford]] city centre|city5=Wolvercote|city6=Oxford Airport|locattion7=[[Woodstock, Oxfordshire|Woodstock]]|city8=Swindon}}
|notes=Swindon signed eastbound only; eastern terminus of A44; northern terminus of A4144
}}
{{GBRint
|type=incomplete
|location_special=[[South Leigh]]-[[Witney]] boundary
|mile=66.2
|road={{Jct|country=GBR|B|4022|location1=[[Witney]] East}}
|notes=Grade-separated junction; westbound exit and eastbound entrance
}}
{{GBRint
|location_special=[[Witney]]-[[Ducklington]] boundary
|mile=68.0
|mile2=68.4
|road={{Jct|country=GBR|A|415|A|4095|to2=yes|city1=Witney|location2=[[Abingdon-on-Thames|Abingdon]]|city3=Faringdon}}
|notes=Grade-separated junction; To A4095 and Faringdon signed westbound only
}}
{{GBRint
|type=incomplete
|location_special=[[Brize Norton]]-[[Minster Lovell]] boundary
|mile=70.8
|road={{Jct|country=GBR|B|4477|location1=[[Carterton, Oxfordshire|Carterton]]|city2=RAF Brize Norton|city3=Minster Lovell}}
|notes=Grade-separated junction; westbound exit and eastbound entrance
}}
{{GBRint
|location=Burford
|mile=74.8
|road={{Jct|country=GBR|A|361|A|424|name1=The Hill|to2=yes|city1=Lechlade|city2=Chipping Norton|location3=[[Stow-on-the-Wold|Stow]]|city4=Burford|city5=Faringdon}}
|notes=Faringdon signed eastbound only
}}
{{GBRint
|county=Gloucestershire
|cspan=13
|location_special=[[Northleach with Eastington]]-[[Hampnett]] boundary
|mile=83.9
|road={{Jct|country=GBR|A|429|city1=Cirencester|location2=[[Stow-on-the-Wold|Stow]]|city3=Northleach|city4=Bibury|city5=Turkdean|location6=[[Bourton-on-the-Water|Bourton]]}}
|notes=
}}
{{GBRint
|type=concur
|location_special=[[Shipton, Gloucestershire|Shipton]]
|mile=89.9
|road={{Jct|country=GBR|A|436|road|[[Shipton, Gloucestershire|Shipton]]|A|417|dir1=west|to3=yes|city1=Gloucester|location2=[[Kilkenny, Gloucestershire|Kilkenny]]}}
|notes=Eastern terminus of A436 concurrency
}}
{{GBRint
|type=concur
|location=Andoversford
|mile=90.7
|road={{Jct|country=GBR|A|436|dir1=east|city1=Stow-on-the-Wold|city2=Bourton-on-the-Water}}
|notes=Western terminus of A436 concurrency
}}
{{GBRint
|type=concur
|location_special=[[Charlton Kings]]-[[Cheltenham]] boundary
|mile=95.8
|road={{Jct|country=GBR|A|435|road|Haywards Road|dir1=south|name1=Cirencester Road|city1=Cirencester|location2=[[Seven Springs, Gloucestershire|Seven Springs]]|city3=Colesbourne}}
|notes=Information signed eastbound only; eastern terminus of A435 concurrency
}}
{{GBRint
|type=concur
|location=Cheltenham
|lspan=3
|mile=96.1
|road={{Jct|country=GBR|A|435|B|4632|dir1=north|name1=London Road|to2=yes|location1=[[Cheltenham]] town centre|city2=Evesham|location3=[[Broadway, Worcestershire|Broadway]]|location4=[[Prestbury, Gloucestershire|Prestbury]]|city5=Winchcombe}}
|notes=Information signed westbound only; western terminus of A435 concurrency
}}
{{GBRint
|mile=97.0
|road={{Jct|country=GBR|A|46|name1=Bath Road|city1=Stroud|city2=Leckhampton|city3=Shurdington|city4=Birdlip}}
|notes=
}}
{{GBRint
|mile=98.8
|road=Princess Elizabeth Way ([[A4013 road|A4013]] north) - [[Swindon Village]]
|notes=Southern terminus of A4013
}}
{{GBRint
|location_special=[[Badgeworth]]–[[Churchdown]] boundary
|mile=100.1
|mile2=100.7
|road={{Jct|country=GBR|M|5|location1=[[South West England|The South West]]|city2=Midlands|city3=Tewkesbury|city4=Bristol}}
|notes=The South West and Midlands signed westbound only; Tewksbury and Bristol eastbound only; M5 junction 11
}}
{{GBRint
|location=Gloucester
|lspan=3
|road={{Jct|country=GBR|A|417|B|4063|dir1=south-east|name2=Cheltenham Road|city1=Cirencester|city2=Hucclecote|city3=Longlevens|city4=Churchdown|city5=Innsworth|extra=airport}}
|notes=Airport signed eastbound only
}}
{{GBRint
|mile=104.5
|road={{Jct|country=GBR|A|38|name1=Tewksbury Road|city1=Gloucester|city2=Tewkesbury|city3=Twigworth|location4=[[Longford, Gloucestershire|Longford]]}}
|notes=
}}
{{GBRint
|mile=105.8
|road={{Jct|country=GBR|A|417|M|50|dab2=Great Britain|to2=yes|city1=Ledbury|city2=Gloucester|city3=Hartpury|city4=Maisemore}}
|notes=
}}
{{GBRint
|location=Highnam
|mile=107.3
|road={{Jct|country=GBR|A|48|dir1=west|city1=Chepstow|city2=Westbury-on-Severn|city3=Minsterworth}}
|notes=Eastern terminus of A48
}}
{{GBRint
|location_special=[[Huntley, Gloucestershire|Huntley]]
|mile=112.3
|road={{Jct|country=GBR|A|4136|A|466|dir1=west|name1=Longhope Road|to2=yes|city1=Monmouth|city2=Chepstow|city3=Cinderford|city4=Mitcheldean}}
|notes=To A466, Monmouth, and Chepstow signed westbound only; eastern terminus of A4136
}}
{{GBRint
|type=concur
|county=Herefordshire
|cspan=3
|location=Ross-on-Wye
|mile=121.4
|road={{Jct|country=GBR|A|449|road|Ledbury Road|M|50|dab3=Great Britain|dir1=north|to3=yes|city1=Midlands|location2=[[Worcester, England|Worcester]]|city3=Ross-on-Wye}}
|notes=Eastern terminus of A449 concurrency
}}
{{GBRint
|location_special=[[Wilton, Herefordshire|Wilton]]
|mile=122.8
|road={{Jct|country=GBR|A|49|B|4260|dir1=north|name2=Wilton Road|city1=Hereford|city2=Ross-on-Wye|location3=[[Wilton, Herefordshire|Wilton]]}}
|notes=Wilton signed eastbound only; southern terminus of A49
}}
{{GBRint
|location_special=[[Whitchurch, Herefordshire|Whitchurch]]
|mile=127.6
|mile2=127.7
|road={{Jct|country=GBR|A|4137|B|4229|to2=yes|city1=Hereford|location2=[[Goodrich, Herefordshire|Goodrich]]|location3=[[Symonds Yat]] (east)}}
|notes=Grade–separated junction; southern terminus of A4137
}}
{{jctbridge
|county_special=[[Herefordshire]]–[[Monmouthshire]] county boundary
|location_special=[[Ganarew]]–[[Monmouth]] boundary
|mile=130.5
|bridge=[[England–Wales border]]
}}
{{GBRint
|county=Monmouthshire
|cspan=5
|location=Monmouth
|lspan=2
|mile=131.8
|mile2=132.4
|road={{Jct|country=GBR|A|466|A|4136|to2=yes|city1=Monmouth|city2=Chepstow|city3=Forest of Dean}}
|notes=
}}
{{GBRint
|type=incomplete
|mile=132.9
|road={{Jct|country=GBR|B|4293|B|4233|to2=yes|city1=Monmouth|city2=Trellech|location3=[[Rockfield, Monmouthshire|Rockfield]]}}
|notes=Grade-separated junction; To B4233 and Rockfield signed westbound only; no westbound entrance
}}
{{GBRint
|type=concur
|location_special=[[Mitchel Troy]]–[[Raglan, Monmouthshire|Raglan]] boundary
|mile=138.8
|mile2=139.2
|road={{Jct|country=GBR|A|449|M|4|dir1=south|to2=yes|location1=[[Newport, Wales|Newport]]|city2=Cardiff}}
|notes=Grade-separated junction; Cardiff signed westbound only; western terminus of A449 concurrency
}}
{{GBRint
|location_special=[[Llanfoist Fawr]]–[[Abergavenny]] boundary
|mile=147.6
|mile2=147.9
|road={{Jct|country=GBR|A|465|A|4042|name1=Heads of the Valleys Road|dir2=south|city1=Merthyr Tydfil|city2=Hereford|location3=[[Newport, Wales|Newport]]|city4=Pontypool}}
|notes=Pontypool signed westbound only; northern terminus of A4042
}}
{{GBRint
|location=Abergavenny
|mile=149.5
|road={{Jct|country=GBR|A|4143|road|MT Street|A|465|dir1=south|to3=yes|city1=Llanfoist|location2=[[Merthyr Tydfil|Merthyr]]}}
|notes=Northern terminus of A4143
}}
{{GBRint
|county=Powys
|cspan=6
|location=Crickhowell
|mile=155.2
|road={{Jct|country=GBR|A|4077|dir1=south|name1=New Road|location1=[[Llangattock, Powys|Llangattock]]|city2=Gilwern}}
|notes=Northern terminus of A4077
}}
{{GBRint
|location_special=[[Cwmdu, Powys|Cwmdu]]
|mile=156.7
|road={{Jct|country=GBR|A|479|A|470|dir1=north|to2=yes|city1=Builth Wells|city2=Tretower|location3=[[Cwmdu, Powys|Cwmdu]]|city4=Talgarth}}
|notes=Southern terminus of A479
}}
{{GBRint
|type=concur
|location=Llanfrynach
|mile=166.7
|road=[[Llanfrynach]], [[Groesffordd]], [[Llangors]], [[Pencelli]]
|notes=Grade–separated junction
}}
{{GBRint
|type=concur
|location=Brecon
|lspan=2
|mile=167.4
|road={{Jct|country=GBR|A|470|B|4601|dir1=north|city1=Builth Wells|city2=Brecon}}
|notes=Eastern terminus of A470 concurrency
}}
{{GBRint
|type=concur
|mile=169.8
|road={{Jct|country=GBR|A|470|B|4601|dir1=south|city1=Cardiff|location2=[[Brecon|Llanfaes]]}}
|notes=Western terminus of A470 concurrency
}}
{{GBRint
|location=Sennybridge
|mile=177.2
|road={{Jct|country=GBR|A|4067|dir1=south|city1=Ystradgynlais|city2=Swansea}}
|notes=Northern terminus of A4067
}}
{{GBRint
|county=Carmarthenshire
|cspan=12
|location=Llandovery
|lspan=2
|mile=189.7
|road={{Jct|country=GBR|A|4069|dir1=south|name1=Broad Street|city1=Llangadog}}
|notes=Northern terminus of A4069
}}
{{GBRint
|type=concur
|mile=189.9
|road={{Jct|country=GBR|A|483|dir1=north|name1=New Road|city1=Builth Wells}}
|notes=Eastern terminus of A483 concurrency
}}
{{GBRint
|location=Llanwrda
|mile=193.9
|road={{Jct|country=GBR|A|482|dir1=north-west|city1=Lampeter|city2=Pumsaint}}
|notes=South-eastern terminus of A482
}}
{{GBRint
|location=Llansadwrn
|mile=196.3
|road={{Jct|country=GBR|A|4069|name1=Station Road|city1=Llangadog|city2=Brynamman|location3=[[Bethlehem, Carmarthenshire|Bethlehem]]}}
|notes=
}}
{{GBRint
|type=concur
|location=Manordeilo and Salem
|mile=201.5
|road={{Jct|country=GBR|A|483|M|4|dir1=south|name1=Rhosmaen Street|to2=yes|city1=Llandeilo|city2=Swansea}}
|notes=Western terminus of A483 concurrency
}}
{{GBRint
|location=Carmarthen
|mile=214.8
|road={{Jct|country=GBR|A|485|A|484|dir1=north|to2=yes|city1=Lampeter|location2=[[Cardigan, Ceredigion|Cardigan]]|extra=hospital}}
|notes=Southern terminus of A485
}}
{{GBRint
|type=concur
|location=Llangunnor
|lspan=2
|mile=216.2
|road={{Jct|country=GBR|A|484|B|4300|dir1=north|name2=Heol Llangynnwr|location1=[[Carmarthen]] town centre|city2=Llangunnor}}
|notes=Eastern terminus of A484 concurrency
}}
{{GBRint
|type=concur
|mile=216.7
|road={{Jct|country=GBR|A|48|A|484|M|4|dir1=east|dir2=south|to3=yes|city1=Swansea|city2=Llanelli|city3=Burry Port|city4=Kidwelly}}
|notes=Western terminus of A484 concurrency; western terminus of A48
}}
{{GBRint
|location=Carmarthen
|lspan=3
|mile=217.2
|road={{Jct|country=GBR|A|4242|dir1=east|location1=[[Carmarthen|Town centre]]}}
|notes=Western terminus of A4242
}}
{{GBRint
|type=incomplete
|mile=217.6
|mile2=217.8
|road={{Jct|country=GBR|B|4312|location1=[[Carmarthen|Johnstown]]}}
|notes=[[Interchange (road)|Grade-separated junction]]; no eastbound exit
}}
{{GBRint
|mile=218.4
|mile2=218.5
|road=[[Llanllwch]] to {{Jct|country=GBR|B|4312|location1=[[Carmarthen|Johnstown]]}}
|notes=Grade-separated junction; To B4312 and Johnstown signed eastbound only
}}
{{GBRint
|location=St Clears
|mile=225.5
|mile2=225.9
|road={{Jct|country=GBR|A|477|A|4066|A|478|dir1=west|dir2=south|to3=yes|city1=Pembroke Dock|city2=St Clears|city3=Laugharne|city4=Pendine|city5=Tenby}}
|notes=To A478 and Tenby signed westbound only; eastern terminus of A477; northern terminus of A4066
}}
{{GBRint
|county=Pembrokeshire
|cspan=6
|location_special=[[Llanddewi Velfrey]]–[[Narberth, Pembrokeshire|Narberth]] boundary
|mile=235.9
|road={{Jct|country=GBR|A|478|location1=[[Cardigan, Ceredigion|Cardigan]]|location2=[[Narberth, Pembrokeshire|Narberth]]}}
|notes=
}}
{{GBRint
|location=Llawhaden
|mile=239.3
|road={{Jct|country=GBR|A|4075|B|4314|A|477|dir1=south|to3=yes|city1=Pembroke Dock|city2=Tenby|city3=Robeston Wathen|city4=Llawhaden}}
|notes=Northern terminus of A4075
}}
{{GBRint
|location=Haverfordwest
|mile=246.2
|mile2=247.4
|road={{Jct|country=GBR|A|487|A|4076|dir1=north|dir2=south|city1=Haverfordwest|location1=Town centre|city2=Milford Haven|city3=St Davids}}
|notes=St Davids signed westbound only; southern terminus of A487; northern terminus of A4076
}}
{{GBRint
|location=Scleddau
|mile=258.8
|road={{Jct|country=GBR|A|4219|A|487|dir1=north|to2=yes|city1=St Davids}}
|notes=Southern terminus of A4219
}}
{{GBRint
|location=Fishguard and Goodwick
|mile=260.0
|mile2=261.2
|road={{Jct|country=GBR|A|487|city1=Fishguard|location2=[[Cardigan, Ceredigion|Cardigan]]|city3=St Davids}}
|notes=Western terminus
}}
{{jctbtm|keys=incomplete, concur}}

==Gallery==
<gallery>
Image:High Holborn 1.jpg|[[High Holborn]]
Image:New Oxford Street 1.jpg|[[New Oxford Street]]
image:marble.arch.london.arp.jpg|[[Marble Arch]]
Image:Hoover Building 1.jpg|The [[Hoover Building]] as seen from the A40 Western Avenue in [[Perivale]] 
File:The A40 at Monmouth - geograph.org.uk - 606053.jpg|A40 at [[Monmouth]]
File:The last few metres of the A40, Fishguard - geograph.org.uk - 1512235.jpg|Western end of A40 at Goodwick
</gallery>

==See also==
* [[British road numbering scheme]]
* [[Trunk roads in Wales]]
{{commons category}}

==References==
{{Reflist}}

==Further reading==
* Edward Platt, ''Leadville: A Biography of the A40'' (Picador, 2001). {{ISBN|0-330-39263-8}}.

{{GB A road zone 4}}
{{Motorways and Trunk Roads in England}}
{{Motorways and Trunk Roads in Wales}}
{{Transport in Buckinghamshire}}
{{Transport in Carmarthenshire}}
{{Transport in Gloucestershire}}
{{Transport in Monmouthshire}}
{{Transport in Pembrokeshire}}
{{Transport in Powys}}
{{Authority control}}

{{DEFAULTSORT:4-0040}}
[[Category:Constituent roads of European route E30]]
[[Category:Roads in Buckinghamshire]]
[[Category:Roads in Carmarthenshire]]
[[Category:Roads in Gloucestershire]]
[[Category:Roads in Herefordshire]]
[[Category:Roads in London]]
[[Category:Roads in Monmouthshire]]
[[Category:Roads in Oxfordshire]]
[[Category:Roads in Pembrokeshire]]
[[Category:Roads in Powys]]
[[Category:Roads in the Brecon Beacons National Park|40]]
[[Category:Streets in the London Borough of Camden]]
[[Category:Streets in the London Borough of Ealing]]
[[Category:Streets in the London Borough of Hammersmith and Fulham]]
[[Category:Streets in the London Borough of Hillingdon]]
[[Category:Streets in the Royal Borough of Kensington and Chelsea]]
[[Category:Streets in the City of Westminster]]