|Location Map ( geo)|
|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.
|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|