During navigation why does it sometimes say the destination is in restricted access? Or something to that effect.

 

Private roads, maybe or Bus, Ambulance only

 

From my experience it can include the following:
- pedestrian street
- boomed-off area
- gated community
- secured area (factory, military, etc.)
- parking lot (think shopping mall, shopping plaza, etc)

And there have been times this message came up for no reason I could discern.
In general, I simply ignore it.

 

It's a general warning that you may not be able to drive there. For example access could be time restricted, or you need a permit, or private road as mentioned above and related things. Basically getting there involves roads or access that may not be publicly accessible at all times. Especially in European cities there are increasingly special zones that you are only allowed to drive in if you have a permit, or your car meets certain emissions requirements.

 

All good examples above. To give a specific case where this happens for me: We have carpool lanes (2 or more occupants, or you can have a registered transponder and pay a toll each time you enter solo) and when using navigation and I enter the carpool lane, I will get that message.

 

The carpool message is a different message. The one OP is referring to I believe is the one you get at the beginning of the route if the destination is in a restricted area. The carpool restriction warning comes on at the time it suggests you enter the carpool lane. In the settings you can specify the number of occupants, too, so it only includes the carpool lanes if you have enough occupants.

 

That's quite possible, I generally don't use MB Nav that much. I work on a base, and I had to go to a different base for reasons and used MB Nav and I believe I got the message as stated by the OP.