He pulled up and got out to tell them to stop when two people on a yellow Peugeot moped arrived on the scene.
The moped’s pillion passenger, a boy aged about 17, first had what police describe as a “verbal altercation” with the motorist.
He is then alleged to have attacked him before trying to steal his car keys.
The boy also jumped on the car’s bonnet and stamped on its windscreen until it smashed.
He is described as white, skinny and about 5ft 9in tall. He was wearing a grey hooded jacket and black jogging bottoms.
Anyone with information is asked to ring Humberside Police on 101, quoting log reference 16/27572/18.