The busy road between Aylesbury and Bicester will be shut for HS2 work from Monday night.
A stretch of the A41 near Westcott is expected to be closed from tomorrow (Monday) from 7pm until 6am for the next few nights.
Motorists are being warned that the diversions will use country roads that may not be gritted if the temperatures fall, and that extra care should be taken when going through the villages. It's also possible that joggers or dog walkers could be using the routes in the evening or early in the morning.
It's unclear at this stage how many nights the road will be shut off for.