Around 249 cities around the world have a trolleybus system currently operating. More than one third of those cities are in Russia and Ukraine, and more than half of the revenue lines are in those countries. Trolleybuses are still common in Central and Eastern Europe and China, while in the Western world they have mostly been replaced by buses and did not experience a resurgence since the late 20th century like tram/light rail technology did. Notable exceptions in the western world are Italy and Switzerland.