Dublin is served by a network of nearly 200 bus routes which cover the city and suburbs. The majority of these are provided by Dublin Bus, with a modest number having been transferred to Go Ahead Ireland in 2018. A number of smaller companies also operate. Fares are generally calculated on a stage system based on distance travelled. There are several different levels of fares, which apply on most services. A "Real Time Passenger Information" system was introduced at Dublin Bus bus stops in 2012 in which signs relay display the projected time of the next buses' arrival based on its GPS position. The National Transport Authority is responsible for integration of bus and rail services in Dublin and has been involved in introducing a pre-paid smart card, called a Leap card, which can be used on all of Dublin's public transport services.