A man heading to a ferry port went missing after the bus he was travelling on stopped at a service station.
Henry Fullaton, also known as Davey, from Glasgow, was on the coach to Hull when the vehicle stopped at Wetherby Services on the A1 at around 4.30pm on Tuesday.
The 68-year-old left his belongings on the bus - including his phone, passport, bag and medication - but did not return to collect them or continue his journey.
Searches have been carried out around the area in North Yorkshire with help from the National Police Air Service's helicopter.
A possible sighting was made at junction 47, where the A1 links to the A59 to York and Harrogate, with searches continuing there.
Officers are appealing for any information from anyone who may have seen Mr Fullaton at the services or along any of the nearby roads, or someone who may have offered him a lift.
He is described as white, around 5ft 7in and of medium build, with brown hair, and unshaven with stubble.
He was wearing glasses and a grey top.
North Yorkshire Police are asking anyone with information to call 999.