The injured man is believed to have suffered head, pelvic and leg injuries following the incident in Easington Road, Hartlepool, on Thursday, June 23, at around 8.30pm.
He was a passenger on a motorbike involved in a collision with a black Range Rover.
Police say the “a 20-year-old man who was on the motorbike has been arrested in connection with the incident” and that the car said to be involved “made off from the scene”.
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The road remained closed on Friday morning and a forensics tent could be seen at the scene.
Cleveland Police said in a statement: “Police received a report of a collision on Easington Road, Hartlepool, around 8.30pm last night, Thursday, 23rd June, involving a black Range Rover and a motorbike.
“A man in his 20s who was on the motorbike was taken to hospital for treatment with suspected head, pelvic and leg injuries.
“A 20-year-old man from the motorbike has been arrested in connection with the incident. He remains in police custody at this time.
“The Range Rover believed to be involved made off from the scene.
“The road remains closed at this time whilst inquiries are being carried out.
“Officers are appealing for CCTV and dash cam footage and they also want to speak to any witnesses.
“Anyone with information is asked to contact Cleveland Police on 101, quoting incident number 108131.
“Footage can also be uploaded here: https://unitedkingdom1cpp-portal.digital-policing.co.uk/cleveland/appeal/appeal-after-collision-in-hartlepool”