Outside Santa Cruz, Bolivia's most populous city, the highway starts to resemble a parking lot with dozens of cargo-laden trucks stopped in a long line as exhausted-looking drivers wait by the side of the road. Wet clothing hangs from the windows of some trucks.
The vehicles are blocked by large mounds of sand piled on the highway as it passes through the town of San Carlos, 68 miles (110 kilometers) from Santa Cruz. No cars or trucks pass the mounds, only motorcycles transporting people.
