A vehicle's speed on a Nav V is displayed in separate two ways:
1. On the dashboard, where the current speed of the bike is displayed alongside what Garmin believes is the speed limit. If you exceed the limit, the bike's speed turns to red. On the continent, you can leave the unit alone, as it will adjust automatically. For instance, a 50 kph limit will display as 31 mph. This saves bikermates the angst of changing their instruments or calculating a number in their head as they hoon their awesome steeds. On an unlimited German autobahn, the display of the road's limit vanishes, leaving you with just the vehicle's current speed. Obvious to see why.
The display is always present on the dashboard, irrespective of other settings.
2. On the screen itself, when running a route. Sometimes this display vanishes, I have no idea why. Maybe because Garmin does not know the road's speed limit? Maybe it just gets bored?