From Opatija you can travel by bus to Lucerne via Rijeka, during summer season there is daily departure from Rijeka, during winter season several times weekly, to get to Rijeka from Opatija you have to take local bus (Travel time about 15 minutes), at the bus station in Rijeka you can then board the bus to Lucerne. If you also plan to travel from Lucerne to Opatija (Rijeka) you should buy a discount return ticket, below you can see timetable for buses between Rijeka and Lucerne.