If you work with them on staying close to the handler then you can track with them off lead just about like they were attached to a lead. They just learn that you're working as a team and they're not allowed to tear out on their own. There's pros and cons to doing it this way. My dogs aren't gonna take a wounded deer and run him the same as some dogs will but the upside to that is that I'm able to track in areas around roads and subdivisions, etc with the confidence that I can let them search off lead.