A woman walking the Cleveland Way in North Yorkshire suffered serious injuries when she was hit by a motorcyclist who fled the scene.
Police said the 75-year-old woman, from Warwickshire, was hit by a "large sports bike" on the B1257, near the village of Chop Gate on Sunday evening.
Officers said the biker stopped a short distance away before leaving the scene in the company of a second rider.
The woman was taken to James Cook Memorial Hospital in Middlesbrough.
Officers said the biker involved in the accident left the scene in the direction of Stokesley.
A police spokesman said neighbouring forces were being contacted for help in tracing the bike.
He said: "The rider did nothing to find out how the woman was or help her.
"I would appeal to the rider - or the second biker - to contact us.
"These actions will not be tolerated."