TRIPOLI—Libyans watching a peace process nearing a critical phase this week in Switzerland need only try driving from one side of their country to the other to understand the obstacles to diplomacy. An October ceasefire called for all foreign mercenaries to leave the country and for the main coastal road between west and east to reopen. But the mercenaries remain, the United Nations said last week, and the road is shut. For those who cannot take one of the flights that resumed last year between the capital Tripoli in the west and Benghazi in the east, it means a long, dangerous detour through the desert. “Drivers face violence and abuse. Sometimes we lose contact with the drivers for two days until they reach safety and can get a mobile signal,” said a transport company worker, who asked not to be named fearing reprisals from armed groups. A 24-year-old driver from …