Vehicles can display speed limits from both sources, depending on the features fitted to the vehicle. Modern sat nav systems can provide speed limit information provided by the navigation data, while traffic sign recognition systems can 'read' speed limit signs and display this information to the driver. However, both of these systems have the potential to be incorrect - even if you keep your navigation up to date with the latest map version it can still lag behind reality when a speed limit has been changed. Similarly TSR systems are not flawless and can be confused by other signs.