Northumbria Police said officers received a report shortly before 3.30pm on Saturday of a serious assault at Whiteleas Way roundabout, at the junction with Nevinson Avenue, in South Shields.
An altercation was said to have taken place between a man in a Nissan Micra and a man travelling on a mobility scooter.
The man in the car allegedly got out and punched the victim in the head and neck, causing him to fall to the ground.
Emergency crews attended and the victim – a man in his 60s – was taken to hospital with serious head injuries, where he remains in a critical condition.
A man in his 70s was arrested on suspicion of causing grievous bodily harm with intent, police said.
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The suspect has been released on bail pending further inquiries.
The force has appealed to the public for information, saying it is “keen to trace any witnesses who were in the area at the time”.
