Anthony Brown was reported missing on Sunday after he was last seen at Higham train station in Kent last Thursday.
CCTV footage has now been released which shows Mr Brown boarding a train at 4.50pm which arrived at Northfleet train station at 5.02pm.
Mr Brown, who is from Reading, had been in the area after his car had broken down on the M25.
He is described as white, five feet 10 ins and medium build with grey hair and grey/blue eyes.
He was last seen wearing grey trousers, brown shoes with white socks, a burgundy jumper and a long checked beige coat. He was also using a walking stick.
Investigating officer Insp Lee Cheesman said: ‘We now know that Mr Brown got off the train at Northfleet station at around 5pm but we do not know where he went to next.
‘While he may have travelled on another train and maybe elsewhere, I want to ask everyone in the Northfleet area to check their garden sheds and outbuildings, in case he may need assistance. We are carrying out a thorough search to locate Mr Brown.’
Mr Brown has links to Gravesend, Woodley in Berkshire and Richmond. He may also have travelled to Surrey.
Anyone with information is asked to call 999 quoting reference 21-1299.
