The A2 is shut in both directions after a crash near Brenley Corner.
A road sweeper and a lorry collided on the London-bound carriageway some 550 yards from the junction with the M2 and A299 Thanet Way.
It happened at 4.25pm. Three fire engines, Kent Police and SECAmb are in attendance.
The accident is causing delays all the way back to junction with the A28 at Thanington and Wincheap.
Highways England is warning drivers to expect delays and urging them to avoid the area.
It said: “Road users travelling eastbound from the M2 are being diverted off at J7 (Brenley) of the M2 then re-enter the M2 westbound and then exit on to the A251 towards Ashford.
“Non motorway traffic will be directed on to the A2 westbound at Brenley. All routes lead to the A251. At the junction of the A251/A252 diverted traffic will exit the roundabout on to the A252 (eastbound) towards Canterbury.
“The A252 merges with the A28. Continue on the A28 towards Thannington then re-join the A2 eastbound.