When you drive into Swansea on the M4 via junction 44 or 45, you'll drive under a fair number of bridges and flyovers. From underneath, it's hard to actually see what they are - but you might've noticed one which no cars or trains ever cross.
Between the two junctions there's a concrete bridge which, from below, looks slightly worn but otherwise inconspicuous. But one motorway fanatic took it upon himself to clamber through the trees to see what it was all about - and found an abandoned railway running across it.
In one video, covering some of the M4's quirkiest roundabouts and slip roads, Auto Shenanigans host Jon discovers a bridge heading over the M4 that seems to go nowhere. Dense trees and bushes cover the path on either side, and the bridge can be seen from both the M4 and nearby Ynysallan Road.
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A view from above on Google Maps shows railway tracks running over the bridge, which upon further investigation are still there despite not being linked to a modern-day railway. In the video, Jon asks: "What's this railway all about?
"Well, it's a branch line that came off the main line built by GWR. From here, the railway would've headed north towards Clydach and where today we find a housing estate, back in the 1930s you'd have found several sidings that were built to serve a gravel pit."
Railmaponline's map of historic railways shows the outline of a partly-built line that likely would've passed through Clydach on its way from Felin Fran Halt, Llansamlet, to Gwaun-Cae-Gurwen, NPT.
We sent a photographer to take a look at the bridge and he saw the tracks - fully intact but slightly overgrown with weeds and twigs. At one end it's gated off, and from the motorway below it still looks like any ordinary bridge.
The bridge is one of several quirks of the M4 uncovered by Auto Shenanigans' Jon. One roundabout in Cardiff is the only one of its kind in Wales - you can read more about that here.
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