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Tredegar Park Interchange

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Tredegar Park Interchange
Parc Tredegar
Location Map ( geo)
M4 eastbound approaching junction 28 - Geograph - 545650.jpg
Cameraicon.png View gallery (2)
Tredegar Park, Newport
Highway Authority
Welsh Government
Junction Type
Modified Roundabout Interchange
Roads Joined
M4, A48, A467
Junctions related to the A467

Tredegar Park Interchange is junction 28 of the M4 and was originally opened in 1967 when it was the western terminus of the M4. The interchange takes its name from Tredegar House and Park situated to the south-east of the roundabout.


As part of the Severn Bridge approach road contracts, the motorway on the western side of the bridge was originally proposed to extend as far as junction 24 Coldra. During construction of the bridge it was subsequently decided to extend the motorway around the north side of Newport to a new roundabout junction on the A48 at its junction with the then A4072 at Tredegar Park.

The 1967 junction comprised a 4 arm roundabout, with the south and east arms being the A48, the western arm being the A4072 and the northern arm being the dual two-laned M4. Note that whilst convention dictates that the M4 runs from east-west and this article refers to east- and west-bound carriageways, the M4 actually runs almost north-south at this point.

When the M4 wes extended to junction 29 and Junction 29A in 1977, the Tredegar Park interchange was modified to suit the new arrangement. The motorway now bypasses the roundabout to the west, with the original westbound carriageway forming the westbound off-slip. Slip roads from and to the eastbound carriageway each pass under the M4, the off-slip merging with the A48 eastbound carriageway shortly before it arrives at the roundabout, whilst the on-slip leaves the roundabout at the start of the original eastbound M4 carriageway before diverting west under the M4. The westbound on-slip diverges from the westbound A48 just to the south of the roundabout.

Finally, the A4072 was renumbered to A467 and the dual carriageway extended up the west-side of the Ebbw river valley, replacing the old A467 which met the M4 at junction 27. (Timescale unknown at the time of writing).


The M4 embankment at junction 28 runs across the historic driveway to Tredegar House, and an Avenue of trees can be seen in both directions from the M4.


Route To Notes


Cardiff / Caerdydd


London, Chepstow


Castleton, St. Mellons, Cleppa Park, Superstore, Imperial Park


Newport / Casnewydd, Hospital


Risca, Brynmawr formerly A4072


  • The M4 Motorway (Eastbound and Westbound Exit Slip Roads at Junction 28 (Tredegar Park Interchange), Newport) (40 MPH Speed Limit) Regulations 2018 - These Regulations impose a maximum speed limit of 40 miles per hour (instead of the general 70 miles per hour speed limit imposed on motorways by the Motorways Traffic (Speed Limit) Regulations 1974 (S.I. 1974/502)) on the lengths of the M4 motorway slip roads specified in the Schedule to these Regulations. These Regulations also amend the M4 Motorway (West of Junction 23A (Magor) to East of Junction 29 (Castleton)) (Variable Speed Limits) Regulations 2015 (S.I. 2015/1018 (W. 72)). The effect of the amendment is to remove a small length of the westbound off slip road at junction 28 (Tredegar Park) of the M4 from the section of road which is subject to a variable speed limit. A maximum speed of 40 miles per hour applies to that length of slip road under these Regulations.


Tredegar Park Interchange
Related Pictures
View gallery (2)
M4 Newport Hard Shoulders.jpgM4 eastbound approaching junction 28 - Geograph - 545650.jpg
Junctions on the M4
Main RouteChiswick • 2 Brentford • 3 Cranford Parkway • 4 Heathrow • 4B Colnbrook • 5 Langley • 6 Tuns Lane • 7 Huntercombe • 8/9 Holyport • 10 Winnersh • 11 Three Mile Cross • 12 Theale • 13 Chieveley • 14 Wickham • 15 Plough Hill • 16 Spittleborough • 17 Stanton St Quinton • 18 Tormarton • 19 Hambrook • 20 Almondsbury • 21 Awkley • 22 Pilning • 23 Rogiet • 23A Magor • 24 Coldra • 25 Caerleon • 25A Grove Park • 26 Malpas • 27 High Cross • 28 Tredegar Park • 29 Castleton • 30 Pentwyn • 31 Junction 31 • 32 Coryton • 33 Cardiff West • 34 Miskin • 35 Pencoed • 36 Sarn • 37 Pyle • 38 Margam • 39 Groes • 40 Taibach • 41 Pentyla • 42 Earlswood • 43 Llandarcy • 44 Lon-Las • 45 Ynysforgan • 46 Llangyfelach • 47 Penllergaer • 48 Hendy • 49 Pont Abraham
Heathrow SpurCherry Lane • 4 Heathrow • 4A Concord
Former RoutesBray • 9A Cox Green • 9B The Thicket // 19 Hambrook • 19A Frenchay // 20 Almondsbury • 21 Aust • 22 Newhouse • 23 Magor // 28  Tredegar Park • 29 St Mellons
Defunct Newport
Bypass Proposal
23 Rogiet • 25 Glan Llyn • 27 Dock Way • 29 Castleton
Junctions on the A48
Highnam Roundabout • Highbeech Roundabout • Parkwall Roundabout • Coldra • Beatty Road Roundabout • Hartridge Farm Road Roundabout • Balfe Road Roundabout • Queensway Meadows Roundabout • Nash Road Roundabout • Church Street Roundabout • Maesglas East • Maesglas West • Ebbw Bridge Roundabout • Tredegar Park • St Mellons • Culverhouse Cross • Sycamore Cross • Waterton Cross • Margam • Groes • Earlswood • Lon-Las • Llangyfelach • Penllergaer • Pont Abraham • Cross Hands • Pensarn