The A10 between Hoddesdon and Broxbourne has been closed by police after what appears to be two separate incidents between the two towns.
A Hertfordshire Constabulary spokeswoman confirmed that police are currently on the scene of what has been reported as a broken down vehicle and a two vehicle road traffic collision.
A spokeswoman said: "A full road closure is in place on the A10. We have a call come in as a car which has broken down as well as a two vehicle RTC on the A10.
"One of the vehicles involved is a Jaguar. Officers at the scene have requested another unit to bring more traffic cones.
"We have a report of a car which has stopped in the fast lane and one which is on the hard shoulder."