A man in his 20s was rushed to hospital with serious injuries after he was hit by a lorry on the A47.
The pedestrian was hit on the eastbound carriageway, close to the junction with the B1146 near Moorgate play area, in the early hours of this morning.
Police were called to the scene at 1.30am.
The man was taken to the Norfolk and Norwich University Hospital with serious injuries to his leg and pelvis.
A spokesperson for Norfolk Police said the road reopened at 7.48am.
On Twitter, Konectbus said their services in the Dereham area are likely to face "significant delays" due to the accident.
Breckland councillor for Dereham Withburga and town councillor, Harry Clarke, said he wished the man a "quick recovery".
He said: "We will have to wait for the police to investigate what happened, but I wish the man a quick recovery.
"I haven't been up that way in a little while but I know there's a public footpath near-by."
Officers would like to hear from anyone who may have witnessed the collision, seen the movements of the pedestrian or the manner of driving of the lorry prior to the collision, or anyone with dashcam footage.
Anyone with information should contact PC James Lister by emailing james.lister@norfolk.police.uk or by calling 101 and quoting reference number NC-03122020-16.
For the latest travel information visit the EDP24 live traffic map
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here