The attack happened on North Leas Avenue between noon and 12.15pm on Sunday.
The victim - a man in his 30s - was punched in the face by the driver of a white Ford Transit van.
He suffered a cut to the mouth and was treated by paramedics.
Police are urging anyone who saw the assault or has dash-cam or CCTV footage of the area from around that time to get in touch.
The suspect is described as being a white man in his mid-50s, of stocky build and around 5ft 6ins tall, with short brown curly hair and a stubble beard. He was wearing dark clothing.
Anyone with information that might help with the investigation should contact North Yorkshire Police on 101, select option two, and ask for PC Daniel Myers.
You can also email [email protected], quoting police reference number 12210095879.
Information can also be passed on anonymously via Crimestoppers on 0800 555111.