At around 10.25pm on Saturday, October 30, a pedestrian was involved in a collision with a car.
Officers from the Beds, Cambs and Herts Roads Policing Unit remain at the scene and the road is closed between the junctions with Station Road and Bedford Street.
People were diverted and unable to go from watford into St Albans road, which had been cordoned off.
Sergeant Sam Cordingley, who is investigating, said: “We know that a motorist slowed down to let the pedestrian cross the road shortly before the collision. I am appealing for that person to come forward as a matter of urgency as they may have information that could greatly assist the investigation.
“I’d also like to hear from anyone who saw what happened or saw the vehicle involved – a grey Audi A3 – or the pedestrian shortly before the collision.”
Anyone with information is asked to contact Sgt Cordingley via the Hertfordshire Constabulary non-emergency number 101, quoting ISR 823 of October 29.
• A man, aged in his 50s and from Edgware, has been arrested in connection with the incident and remains in police custody.