The A5 between Weedon and Kilsby is closed following a serious road traffic accident early this morning.
The crash happened at about 4.25am near to Watford village and involved two vehicles.
A police spokeswoman said: “Emergency services remain at the scene and police are urging motorists to avoid the area for the next few hours, if possible.”
As a result, the A5 is closed in both directions between the A45 High Street junction in Weedon Bec and the A361 junction in Kilsby.
A diversion is in operation via the M1 between J16 and J18.
Reports suggest the accident involved a taxi and a lorry.