Upgrade works to alleviate the severe congestion experienced at this junction on a regular basis.
Winnall Interchange, M3 junction 9, is where the A34 expressway from Oxford and the M40 terminates, and large volumes of traffic negotiate the signalised roundabout between the A34 and the M3 to the south. Several local roads also connect to the roundabout. At present, the majority of green light time is allocated to movements between the M3 and A34, but this causes long delays on other approaches to the junction and is still insufficient to prevent traffic queuing back down the sliproads and onto the mainline of the M3.
No design for the improvement has yet been announced, but it is likely that Highways England are planning to provide free-flowing connections between the M3 to the south and A34 to the north that bypass the roundabout entirely.
A consultation on the proposed route for the upgrading of M3 Junction 9 will run for 6 weeks from Tuesday 9 January to Monday 19 February 2018.
According to the consultation documents, the only option Highways England propose to upgrade the junction will mean new direct free-flow links between the A34 and the M3 to/from the South, just to the north of the current junction. All other movements will be handled by a dumbbell junction, which will replace the existing roundabout - presumably to free up enough space for the new slip roads.
With thanks to Tom Kitcher for information on this page.