The A41 has been closed between the M25 and Berkhamsted after multiple collisions on the dual carriageway.
No one has been seriously injured and police say the stretch of road was closed as a precaution.
But officers are advising motorists across Herts to be extra careful today due to icy conditions.
They say drivers should leave extra time for their journey and drive according to road conditions. Other parts of the county have also been affected by recent icy weather.
Drivers should keep speed down and avoid sudden braking which could result in the loss of control of your vehicle.