The Ring Road is crucially important for domestic and international trade and the economy. A key portion of the Ring Road is the Salang Tunnel, completed in 1964, which facilitates travel through the Hindu Kush mountain range and connects northern and southern Afghanistan. It is the only land route that connects Central Asia to the Indian subcontinent. Several mountain passes allow travel between the Hindu Kush in other areas. Serious traffic accidents are common on Afghan roads and highways, particularly on the Kabul–Kandahar and the Kabul–Jalalabad Road. Traveling by bus in Afghanistan remains dangerous due to militant activities.