Transport in Tanzania includes road, rail, air and maritime networks. The road network is long, of which is classified as trunk road and as regional road. The rail network consists of of track. Commuter rail service is in Dar es Salaam only. There are 28 airports, with Julius Nyerere International being the largest and the busiest. Ferries connect Mainland Tanzania with the islands of Zanzibar. Several other ferries are active on the countries' rivers and lakes. Roads The Tanzania National Roads Agency (TANROADS) - an Executive Agency under the Ministry of Works, Transport and Communications - came into operation in July 2000 and is the agency responsible for the maintenance and development of the trunk and regional road network in Mainland Tanzania. The total classified road network in Mainland Tanzania was estimated to be based on the Road Act 2007. The Ministry of Works through TANROADS is managing the national road network of about , comprising of trunk road and of regional road. The remaining network of about of urban, district and feeder roads is under the responsibility of the Prime Minister's Office Regional Administration and Local Government (PMO-RALG). In 2007 there were of roads, of which including was paved. The road network ranked 51st worldwide by length. Trunk roads Dar es Salaam and Dodoma ( entirely paved): The A-7 road links Dar es Salaam and Morogoro. The B-129 road then connects Morogoro with Dodoma. Dar es Salaam and Iringa ( entirely paved): The A-7 road links these cities. Dar es Salaam and Tanga ( entirely paved): The A-7 road links Dar es Salaam and Chalinze. The A-14 road then connects Chalinze with Tanga. Dar es Salaam and Mtwara ( entirely paved): The B-2 road links these cities. The remainder of the road to Dar es Salaam is paved. The long Mkapa Bridge is on this stretch of road, spanning the Rufiji River. Tanga and Arusha ( entirely paved): The A-14 road connects Tanga and Segera. From there, the B-2 road connects Segera with the road's terminus at the Himo Junction. The A-23 road then leads west to Moshi and Arusha. Dodoma and Mwanza on Lake Victoria ( (entirely paved): The B-129 road leads west to Manyoni, followed by the B-141 road north to Singida. From there, the B-3 road leads mostly west to Nzega. The final stretch is on the B-6 road through Shinyanga to Mwanza. Dodoma and the