The A34 is closed northbound near Oxford after a jackknifed lorry caused a diesel spill.
Drivers are being warned of long delays and are urged to use alternative routes if possible.
The road is currently closed northbound between the A44 Peartree Interchange and the M40 at Junction 9 due to resurfacing work.
A diversion route is currently in place.
Emergency repairs are ongoing, as new tarmac is being laid.
The road is expected to remain closed until at least 18:00 on Friday.