Some UPS drivers use their own GPS devices if they are lost and need to find an address or they might use Google Street View if they are in an area where they are having trouble finding an address.
That is what one UPS driver told me that he did.
UPS trucks also have their own mapping software to help the driver find addresses and when the person loads a UPS truck they load the packages in an order that is delivered on the route as they go down it.
So as they scan someone's package they are then alerted to the next address for the next packages and so on and so forth.
Some drivers have been driving the area for years and know what streets to go down without needing to use the mapping software or GPS but they still have it available.