A man is being treated for a brain injury and multiple facial fractures after being knocked down in Leeds by an off-road motorbike.
The motorbike was said to be performing a wheelie on the wrong side of the road when it crashed into the man in the early hours of Sunday.
Police today said officers found the 35-year-old man seriously injured when they were called to Hollyshaw Lane in Halton shortly after midnight.
The man had been walking along the pavement with his partner, near to the junction with Hollyshaw Street, at the time of the collision.
He appears to have stepped into the road as two off-road motorcycles were approaching heading towards Selby Road.
The rider of one bike performed a wheelie while on the wrong side of the road and ran the man over.
Both motorcycles then left the scene without stopping.
The man is continuing to receive treatment for his injuries at Leeds General Infirmary.
PC Michael Jessop, of West Yorkshire Police Safer Roads and Neighbourhood Support, said: "This was a very serious incident which has left a man with significant injuries and we are currently carrying out a range of enquiries to trace the riders of the two off-road motorbikes involved.
"We would like to hear from anyone who witnessed the incident itself or the circumstances leading up to it or who saw two off-road motorbikes being ridden around the Halton area on Saturday night into Sunday morning."
Anyone with information is asked to contact PC 6221 Jessop at Carr Gate via 101, quoting log number 10 of February 26.
Alternatively, call the independent charity Crimestoppers anonymously on 0800 555 111.