This is the mapping of OSM tags to Garmin options:
|goods||Delivery and Truck|
|access||(applies to everything)|
Older versions of mkgmap have the emergency and delivery flags switched. This was fixed in V1136.
Toll Roads -> toll=yes Highways -> Road classes 3 and 4 Unpaved Roads -> mkgmap:unpaved=yes (apply through style file) Ferry Routes -> mkgmap:ferry=yes (apply through style file)
As of r1425, the mkgmap default style adds mkgmap:unpaved and mkgmap:ferry attributes based on surface=*, highway=* and route=ferry.
Some Tests with BaseCamp 3.0.6
access=destination works for Car hgv=destination works for Truck taxi=destination no effect delivery=destination no effect motorcar=destination works for Car, Truck
access=private works for all modes hgv=private works for Truck taxi=private works for Taxi, Truck delivery=private works for Delivery motorcar=private works for Car
 not reproduceable on Garmin Legend HCX