With a full-scale hyperloop system testing in the Nevada desert, Los Angeles-based Hyperloop One is moving forward with plans to build Elon Musk’s vision for high-speed tubular transportation.

One of the key questions is where the futuristic project would be constructed, and on Thursday, some answers took shape. Hyperloop One has narrowed the field from hundreds of applicants to 10 candidates from five countries — including the 640-mile Texas Triangle route that would connect Dallas-Fort Worth,…