Roads are blocked with heavy traffic as police have cordoned off a section of London Road after a collision between three cars.
Hertfordshire Police was called to the collision, which involved three cars, at 3.39pm today.
The collision - which is on London Road between Hemel Hempstead station and the Aldi supermarket at the junction with Two Waters Road - involved a grey Volvo Estate, a silver Vuaxhall Corsa and black Mercedes Kompressor.
Two of the vehicles are being recovered after the smash according to the police.
There has been no confirmation yet as to whether anyone has been injured in the incident, but motorists are advised to stay away from the road.
A commuter told the Gazette: "We've been stuck here for an hour, it's not moving and it's not good. But the welfare of the people involved is obviously the most important thing, and hopefully they are OK."