The national operators of Denmark and Netherlands have a nationwide system where RFID smartcards are used as train tickets. In the UK, the issuance of printable or mobile tickets is at the discretion of train operators and is often available for advance tickets only (i.e. valid only on a specific train). This is very common in Europe for local urban rail, such as rapid transit/metros.[citation needed] During the 2010:s phone apps have been increasingly popular.