Most major roads were built in the 1960s with assistance from the United States and the Soviet Union. The Soviets built a road and tunnel through the Salang pass in 1964, connecting northern and eastern Afghanistan. A highway connecting the principal cities of Herat, Kandahar, Ghazni, and Kabul with links to highways in neighboring Pakistan formed the primary road system.The network includes 12,350 kilometers of paved roads and 29,800 kilometers of unpaved roads, for an approximate total road system of 42,150 kilometers as of 2006. Traffic in Afghanistan is right hand, with about 731,607 registered vehicles in the country (2008 estimate). The Afghan government passed a law banning the import of cars older than 10 years.Long distant road journeys are made by company-owned Mercedes-Benz coach buses or various types of vans, trucks and private cars. Although a nationwide bus service is available between major cities, flying is safer, especially for foreigners. There are occasional highway robberies by bandits or militant groups. The roads are also dangerous due to accidents and lack of security forces.The highway system is currently going through a reconstruction phase. Most of the regional roads are also being repaired or improved. For the last 30 years, the poor state of the Afghan transport and communication networks have further fragmented and hampered the struggling economy.