Typical uses of PSO include regional airline services in districts of for instance in Northern Norway or Ireland, where the airlines serve marginally populated areas not profitable for the carriers without subsidies. Rail services can be unprofitable even on major routes, and government subsidies are sometimes offered through PSO on unprofitable routes, for instance this has been very popular in Germany. Most cities subsidize their public transport, and in places where the transport is provided by private companies, that may be awarded through PSO. Other common PSO services are ferries, such as the routes to Gotland in Sweden, or car ferries on the road network of Norway. Ferry routes serving outlying islands in Hong Kong are also subsidised since recently, as a result of rising oil price and therefore the costs of operations.