M48

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Route of the M48

The M48 crosses the River Severn alongside the M4. It's an oxbow lake of motorway, being the old route of the M4 across the original Severn Bridge. When the Second Severn Crossing was built, the M4 moved across there, and the M48 took its place.

Despite being effectively bypassed, this little motorway does have a life of its own. It has two of its own junctions, one in England for the A403, making it an easy way into Wales from the industrial areas of Avonmouth, and one in Wales serving Chepstow and the A466. As well as carrying local and commuter traffic, it's also an important diversion route in the event that the Second Severn Crossing is closed.

The Severn Bridge itself makes a journey on the M48 more than worthwhile. The bridge is spectacular. It's not as big as the Second Severn Crossing, whose epic scale makes it a wonder in its own right, but it is particularly handsome and was always far more famous than its newer cousin. The M48 also crosses the Wye Bridge immediately to the west of the Severn, which would — anywhere else — be a famous landmark in its own right. It's a fine cable-stayed bridge that crosses the River Wye and, with it, the border between England and Wales.

Nonetheless, now that it's not the main road any more, it's not a priority for funding. When the motorway's number changed, money was saved on new road signs by just blanking out the first digit of the junction number — the former junction 21 becoming 1 and 22 becoming 2!

The M48 may not be correctly numbered. Despite connecting to the M4 at each end, it lies north of the M4 and west of the M5, so according to the rules established for motorway numbers in the late 1950s, it should really have a number beginning with a 5. It may be that the number M48 was chosen because it connects to the M4 at each end and runs parallel to part of the A48, so while its number may be technically in error, it looks perfectly at home. This numbering oddity is explored in considerable depth in CBRD's pages on Road Numbers.

Factfile

Start Olveston (M4)
Finish Caldicot (M4)
Passes Chepstow
Length 12 miles
Connects to M4

Images

Views of the M48 from on and off the road. If you have a photo to contribute, contact me.

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The Wye Bridge, often-overlooked neighbour of the Severn Bridge. It's just as impressive, with one large cable-stayed span. The Wye Bridge is the one that spans the England-Wales border, and the Severn Bridge is entirely in England.
Photo by Steven Jukes

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From the banks of the river, the Severn Bridge looks deceptively short.
Photo by Steven Jukes

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On the road, it's a different story - it goes on forever! (Especially when one lane is closed, as here).
Photo by Steven Jukes

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Unlike the Second Severn Crossing, you can also walk and cycle across here. All that separates a fast moving motorway and a footpath is one line of steel cabling. You could quite easily step across!
Photo by Steven Jukes

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Heading east from the bridges towards Bristol. Aside from these two magnificent engineering feats, the M48 is actually terribly dull.
Photo by Steven Jukes

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Working on a maintenance project for the Severn Bridge, Alex was given a tour of the structure. Here's one of the formidable towers.
Photo by Alex

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A little higher up, the size of the structure and its colossal support cables becomes clear.
Photo by Alex

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The incredible view from the top, looking towards England.
Photo by Alex

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The view in the other direction, showing the Wye Bridge, and beyond it, Wales.
Photo by Alex

Construction Timeline

When the various parts of the M48 were built, listed in chronological order.

Open Jct Section
Sep1966 Severn and Wye Bridges (Opened as M4; became M48 in 1996)

Exit List

All the junctions and destinations along the route.

Junction   Eastbound               Westbound
(M4 J21)
189.5 km
London
Bristol
M4 Link
M4 EAST
(Fork)
M4 N/A More information about this junction
LanesLanesLanesLanesLanesLanes LanesLanesLanesLanes
2 miles, 2 lanes Up   Down 2 miles, 2 lanes
1
194 km
Severn Beach
A403
Thornbury
B4461
Services Severn View
B4461



Aust Interchange (Roundabout Interchange)Aust Interchange (Roundabout Interchange) A403 Severn Beach
A403
Thornbury
B4461
Services Severn View
More information about this junction
LanesLanesLanesLanes LanesLanesLanesLanes
3 miles, 2 lanes Up  
194.3 km Aust (Toll Plaza) Severn Bridge Toll More information about this junction
LanesLanesLanesLanesSigns
 
River or canal Severn Severn Bridge (Watercourse) River or canal Severn More information about this junction
 
River or canal Wye Wye Bridge (Watercourse) River or canal Wye More information about this junction
  Down 3 miles, 2 lanes
2 Chepstow
Cas-gwent
A466 (A48)
A466
(A48)
Newhouse (Roundabout Interchange)Newhouse (Roundabout Interchange) Chepstow
Cas-gwent
A466 (A48)
More information about this junction
LanesLanesLanesLanes LanesLanesLanesLanes
7 miles, 2 lanes Up   Down 7 miles, 2 lanes
(M4 J23) N/A M4


(Fork)
WEST
M4


Newport
Casnewydd
Cardiff
Caerdydd
M4 Link
More information about this junction
LanesLanesLanesLanes LanesLanesLanesLanesLanesLanesLanes

With thanks to Meic Young for information in this section.