Lawrence Weston Interchange

Gantry for Junction 18a northbound

The Lawrence Weston Interchange is a complex junction between the M5, M49 and Avonmouth Spur, which leads to the A4. For the M5, it is both Junction 18 and Junction 18A on the M5, but has no junction number on the M49. The interchange itself is free-flow and all movements are possible except for vehicles travelling to or from M49 to the M5 (north).

History

The junction spent a few years as a temporary terminus for the M5, here shown on the 1972 OS One Inch sheet

The junction opened as a temporary terminus for the M5 in 1969 with just the two sliproads leading down to the A4 in Avonmouth, resembling a fork. Extra sliproads were added to make it a trumpet when the Avonmouth Bridge opened in 1974. The junction was then left alone for over 20 years.

In 1996 the Second Severn Crossing scheme was being built on the M4. As part of the scheme, a decision was made to build a new motorway to "cut the corner" between the new crossing and the M5, with the advantage of relieving pressure on the existing M5 / M4 junction at the Almondsbury Interchange. This new motorway, numbered M49, met the M5 just to the north of this junction, which was therefore adapted to allow links between the A4 and M5 south and the M49. Since the M49 is designed to link to the new Severn Crossing, there was no reason to add links from the M49 and M5 north.

The two south facing slips remained unchanged, however the north facing slips were radically altered to fit in with the new M49. The onslip was diverted away from joining the M5 immediately, and instead runs parallel before forking. The left fork joins the M49, whilst the right fork passes under the M5 offslip for the M49 to join the M5 itself. Similarly on the southbound carriageway, the M5 diverge was resited some distance to the north. This allowed it to merge with the M49 , so providing both routes with the option to rejoin the M5, or follow the Spur into Avonmouth.

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  The layout of the junction before the M49

• 

  M5 Junction 18 & 18a, present day.

Routes

Route	To	Notes
M5	The MIDLANDS, London (M4 E), Chepstow (M48)
M5	The SOUTH WEST, Weston-s-Mare, Exeter, R. Portbury Dock
M49	SOUTH WALES, Cardiff, Newport (M4 W)	via M4
A4	City centre, Bristol Airport (A38), Park and Ride, Portview, Avon Riverside & Avonbank Ind. Estates
A4	Avonmouth Docks & Trading Estate, Aust, Severn Beach (A403), Avonmouth Village
B4054	Shirehampton, Avonbridge Trading Estate

Links

legislation.gov.uk

• The M5 Motorway (Junction 18 and Avonmouth Relief Road) (Slip Roads, Special Roads) Scheme 1992

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