Called the Herbert Protocol, it is a simple form that family members or carers can fill in at their convenience and keep.
If their relative wanders off, handing it to police can shave vital minutes off their search time because the information is both instant and specific to that person.
Yvonne Lawrence, who has had several worrying experiences with husband Ronald, said she was backing the scheme.
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Yvonne, of St Crispins care village, Northampton, said: "The worst occasion was when I left Ronald in the cafe at Sainsbury's in Sixfields and he went off.
"It turned out that he'd got on three buses and he was gone for three hours in total. That's such a long time to be worrying about someone."
Search experts know that the first hour of someone going missing is a crucial time.
Neil Balderson, of Northamptonshire Search and Rescue, said: "At this time of year, hypothermia can set in very quickly if they walk off unprepared. It's a very high risk to these people."
Search and rescue managers have access to data based on where 56,000 missing people were eventually found, helping them guess where a certain type of person might go.
However, the Herbert Protocol helps them radically narrow down the options, increasing the chances of a happy outcome.
The mathematics of a search operation help prove the point. If someone walks off in an unknown direction, 60 minutes later they can be anywhere in a 12-square mile area.
The Herbert Protocol - named after George Herbert, a Normandy veteran who lived with dementia - allows the search to begin at once, and with highly relevant information. As well as a description, the form might disclose that the missing person liked fishing at a particular spot or used to work at a local factory.
In effect, it shrinks the search area dramatically.
The missing person is not always in danger, however. People with dementia often feel compelled to walk to somewhere that was familiar many years ago.
Inspector Scott Little of Northamptonshire Police said: "Once we were looking for someone and he was walking his old milk round.
"The advice is not to cause extra distress. We informed a family member and they walked with him, completing his round."
However, the Herbert Protocol is set to save family members many agonising minutes or hours.
Yvonne said: "I'll definitely be filling one out, with Ronald's photograph.
"When he goes missing, you get in a bit of a state. This way you have already done the useful bit.
"It's one more thing to help."
Download the Herbert Protocol form at www.northants.police.uk/HerbertProtocol