Re: Covered by GDPR?
Covered by Data Protection Act already. Has been this way for a long time, even for home security cameras.
https://www.gov.uk/request-cctv-footage-of-yourself
If doing facial recognition such that individuals have a personal identifier (some encoded ID based on the shape of their face) then I would think GDPR applies too.
(edit for afterthought:) Is there different legislation for dashcams? If not then how do they meet the requirement about "owner’s details are usually written on a sign attached to the camera"? Or are we all allowed to get car owner's details from DVLA by saying "they had a dashcam, give contact details"?