Surely all you need to do is to google 200, 300, 400 or 600km rides on Strava, and bring up the routes of the well-known rides. You can then see what the best place to start that ride is. Possibly a railway station, a budget hotel, or a safe parking area.
You can then track your ride against somebody else's performance. Following the course of a calendar ride means that you can use online accounts as a guide.
You can work your way up to doing the same with PBP, at a time which suits you, and avoids all the problems of 6,000 others on the road.