The oldest licence holder is a 107-year-old woman, while there are 191 people aged over 100 who have licences.
Once people reach 70 they must declare whether or not they are fit to drive every three years, without having to take a driving or medical examination.
Concerns have been raised that some elderly people could be continuing to drive when they are not fit to do so, while others give up their cars too early and risk exclusion from services and activities.
Research charity Rica - with support from the RAC Foundation - has published a guide to help older people understand the law and find out what modifications they can make to their vehicles and driving habits to keep them on the road for longer.
The publication will also offer advice to elderly people about how best to assess driving capabilities, and how to cope if they do stop driving.
Professor Stephen Glaister, director of the RAC Foundation, said: "All drivers should regularly consider their fitness to drive, but matters come to a head when we reach 70 and have to declare that we should be on the roads.
"For those reliant on a car, giving up driving will have a huge impact on their ability to live an active life, so it is important that they get all the help and support to make the right decision at the right time."
The RAC Foundation found that there are 4,018,900 people aged over 70 with full British driving licences.
The guide, entitled Driving Safely for Life, will be promoted by local authorities, police authorities and community groups.
A Department for Transport spokesman said: "Drivers over 70 must renew their licence every three years and tell the DVLA about any conditions which might affect their driving - most older drivers are aware of their limitations and manage their driving accordingly."