Driving between South Wales and the West Country? The M49 is for you.
Some little motorways have been described as nothing more than glorified sliproads. More than anywhere else, that is true of the M49, which runs for just five miles between the M4 Second Severn Crossing and the M5 at Avonmouth, with no intermediate junctions. It provides a direct route for traffic going between the South West (and Bristol) and Wales, avoiding Almondsbury Interchange. And it does absolutely nothing else. In fact, because it only links the M4 and M5, it is the only motorway in the UK that you can only reach by motorway - there is no way on from ordinary roads.
The junction at the northern end of the M49 has sliproads to provide access in all directions, but the reason for that isn't clear. There's no real reason to allow traffic on or off the M49 from the M4 to the east - anybody doing that would have joined the M5 two junctions previously to reach Avonmouth. The extra sliproads are perhaps to provide a way to avoid the bridge tolls, or perhaps to function as a bypass of the M5 in emergencies, perhaps to provide access to the weighbridge in the middle of the roundabout there - but the most likely reason is that an intermediate junction with a park and ride facility was once planned for the M49.
Plans for the junction were resurrected in 2015, to support expansion of the industrial area next to the motorway at Avonmouth, and if that happens those spare sliproads at the M4 junction will suddenly have a real purpose.
Motorway numbering conventions suggest that - because the M49 lies south of the M4 - it should really have a number beginning with a 3. M39, perhaps?
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