It is more expensive to buy single tickets on board
When buying a single ticket on a bus, tram or boat from zone 1, there is an on board surcharge. This creates a price difference of NOK 20 (NOK 10 for children and concessionary).
On board the train the on board surcharge is NOK 40 from all stations where you can buy a ticket in advance from a ticket machine or booking office. Travelers who are entitled to a concessionary (senior) ticket, or as a result of a disability cannot use the ticket machines, will not be levied on board surcharge.