Star.pngStar.pngStar grey.pngStar grey.pngStar grey.png

Cadnam Interchange

From Roader's Digest: The SABRE Wiki
Jump to navigation Jump to search
Cadnam Interchange
Location Map ( geo)
Start of M27.jpg
Cameraicon.png View gallery (2)
Highway Authority
Highways England
Junction Type
Roundabout interchange
Roads Joined
M27, A31, A336, B3079

Cadnam Interchange is junction 1 of the M27.

It is the only motorway junction inside a national park, though until the national park was created, the New Forest boundary skirted the junction. Despite being the western terminus of the M27, the junction has three lanes through it, but the A31 to the west is only two lanes. This creates a bottleneck where the 3-lane M27 and 2-lane on-slip merge into the 2-lane A31 in a short distance.

Most maps published in the 1970s have this junction shown as having no number, with junction numbering beginning at Ower.


Cadnam used to be a significant settlement on the A31, with a crossroads to the west of the village centre by the St John Barleycorn pub. To create a bypass for Cadnam, that crossroads became a TOTSO, with the A31 being diverted to the south and then along what was effectively a new eastern bypass, now known as Romsey Road and Southampton Road.

To take pressure off the crossroads, the B3078 was diverted west, meeting the A31 in the middle of the current roundabout instead of what is now the pub car park.

With the construction of the M27, the new interchange consumed the diverted course of the B3078. A new dual carriageway link road was built to the east, replacing Southampton Road as it crossed Cadnam Bridge, arriving at an enlarged roundabout. This new route took A31 designation until it was downgraded. It is now hampered by a very sharp bend as it joins the roundabout.


Route To Notes


Southampton, Portsmouth, London For M3 Winchester, The Midlands


Ringwood For A348 Bournemouth, A349 Poole, The West


Cadnam, Copythorne, Ower For A336 Totton, A337 Lyndhurst, The New Forest


Brook, Bramshaw For B3078 Fordingbridge

Cadnam Interchange
Related Pictures
View gallery (2)
Start of M27.jpgA31 eastbound M27 J1.jpg
Junctions on the M27 and spurs
M27Cadnam • 2 Ower • 3 Rownhams • 4 Chilworth • 5 Stoneham • Townhill Park • 7 Hedge End • 8 Windhover • 9 Park Gate • 10 North Hill • 11 Wallington • 12 Paulsgrove • 12 Hilsea
Unbuilt M27:13 Portsbridge • 14 Farlington • 15 Broad Marsh • Langstone • Warblington • Fishbourne Roundabout
M271Redbridge • 1 Nursling • 2 Rownhams • Romsey Road
M275Paulsgrove • Hilsea • 1 Tipner • 2 Rudmore Roundabout
Other spursOwer Rdbt • Swaythling • Portswood • Bevois Valley • Western Terminal • Allington Ln Rdbt • Mousehole Rdbt
Junctions on the A31
Hogs Back • Shepherd and Flock • Hickley's Corner • Coxbridge Roundabout • Chawton Roundabout • Spitfire Roundabout • Bar End • Cadnam  • Rufus Stone • Stoney Cross • Picket Post • Forest Corner • Salisbury Road Junction • Ashley Heath Roundabout • Woolsbridge  Roundabout • Azalea Roundabout • Canford Bottom Roundabout • Red Post • Merley Roundabout

SABRE - The Society for All British and Irish Road Enthusiasts
Home - Discuss - Digest - Discover - Help