There are long delays on the A1 at Grantham after a lorry crashed into the central reservation near the A607 junction.
Traffic is queueing in both directions between the A607 and B1174 junctions.
The lorry was travelling northbound and ended up straddling the central reservation.
There were around 15 litres of diesel spilled on the carriageway.
Only one lane in each direction is open.
Police say the road will not fully re-open before 10pm and are asking drivers to avoid the area.
The driver of the lorry was taken to hospital as a precaution. No other vehicles are believed to have been involved.