The vehicle is blocking the A418 near to the Fairford Leys roundabout in both directions.
The emergency services are on the scene and police are guiding traffic through.
Despite this, Transport for Bucks is advising motorists to avoid the area if at all possible.
Thames Valley Police tweeted: “We are trying our best to clear the traffic from both sides.
“Thankfully no one was seriously hurt.
“Please bear with us.”