The group's principal activities are to construct and to operate mass transit railway system in Hong Kong. The group is comprised of the mtr lines, consisting of the kwun tong line, tsuen wan line, island line, tung chung line and tseung kwan o line and the airport express line. Other activities include development and sale of residential and commercial properties with various third-party developers and manages, and in some cases owns certain developed properties. It also leases advertising and retail space, provides other services within the group network and operates the octopus smart card system which it uses to collect the majority of the fare revenue.
