A dual-mode bus is a bus that can run independently on power from two different sources, typically electricity from overhead lines or batteries, alternated with conventional fossil fuel.
ZiU-9, or ZIU-9 is a Soviet trolleybus vehicle. Other names and indexes for the same vehicle include ZiU-682 and HTI-682. The ZiU acronym stands for Zavod imeni Uritskogo, which is a plant named after Moisei Uritsky, the Russian revolutionary. Before 1996 this acronym was also a trademark of the vehicle manufacturer. It has been changed to Trolza. The ZiU-9 was put in mass production in 1971 and it was still assembled along with other more advanced trolleybus vehicles in the Trolza factory until 2014. The total number of produced ZiU-9s exceeds 42,000 vehicles. In addition, many copies of ZiU-9 were made in other factories of the former Soviet bloc. This model is the most numerous trolleybus vehicle in the world.
The ZiU-5 is a Soviet trolleybus model that was built by the Uritsky factory. The ZiU acronym stands for Zavod imeni Uritskogo, which translates as Plant named after Uritskiy. This model of city trolleybus was in mass production from 1959 to 1972. The total number of ZiU-5s produced exceeded 14,500 vehicles. This allowed the ZiU-5 to become dominant model of trolleybus in Soviet towns and cities of that time. The last vehicles were withdrawn from active service in the mid-1980s. The small number of surviving vehicles are kept now for museum purposes.