Few dash cams show your speed on the screen. The reason is the screen can be considered a distraction - the best place for a dash cam is the top left corner of a windscreen where it can record without obstructing your view of the road. Many of the dash cams display speed (as well as location, date etc) stamps on the footage so these markers can be used by insurers to settle claims faster. As for the Garmin 56, we've not tested it (only the 66W and 55) - but we had no issues at all with them. Very good dash cams in our opinion.

Garmin 55 review: kit.honestjohn.co.uk/reviews/review-garmin-55/

Garmin 66W review: kit.honestjohn.co.uk/reviews/review-garmin-66w/