|Location Map ( geo)|
|Distance:||18.9 miles (30.4 km)|
|Meets:||A30, A3010, B3400, A339, B3051, A4, A329|
|Route outline (key)|
The A340 sits in the middle of two more important routes that lie between the M3 and the M4, namely the A33 and A339. As a consequence, it can be quite a cunning detour if there's a problem on those two roads.
Section 1 : Basingstoke Ringway (West)
The road starts off at the Winchester Road Roundabout, which is at the south western corner of the Basingstoke Ring Road. This first section is dual carriageway and forms the western section of the Basingstoke ring road. On this stretch there are two limited access (only south-facing sliproads) grade-separated junctions with minor roads; in between these junctions is the Thornycroft Roundabout (where it meets the A3010 and B3400). This current roundabout replaced a much larger roundabout / traffic circle (the junction was designed so that entering and circulating traffic would merge smoothly) which was a remnant of the earlier partial cloverleaf here.
At the Newbury Road Roundabout the road meets the A339, which it multiplexes with for a short distance as a D3 with a dedicated lane (westbound this lane is segregated from the main A339 flow by hatching). The route leaves the A339 (which continues as the ring road on a flyover built in 1992/3) at the signalised Aldermaston Road Roundabout. From here there is a short section of recently (2008-9) extended dual carriageway including a couple of traffic light junctions for a hospital and a new housing development before the road leaves the Basingstoke urban area.
Section 2 : Basingstoke - Theale
The road continues northwards through Sherborne St John before meeting Tadley at the Berkshire boundary. Just after this it swings sharply to the left and runs in a straight line between the boundary and the British Nuclear Fuels plant at Aldermaston, famous for not appearing on maps. It then doubles back on itself at a roundabout with the B3051 to circumnavigate the nuclear plant (built on top of its original course) and then passes through Aldermaston village.
The A340 crosses the River Kennet and the main London - Bristol railway at Aldermaston Wharf, before meeting the A4 at a roundabout. From here, it multiplexes with the A4 on a nice wide and partly dualled section (and a surprisingly long multiplex for 1922) up to Theale.
Section 3 : Theale - Pangbourne