From what I know of Japanese coasters, you are correct in the earthquake synopsis. However, there is a simpler, and much funnier reason that those walkways exist. I didn't believe this until I saw it with my own eyes. They use those walkways to wipe the tracks down after heavy rainstorms. In July at Nagashima Spaland, I saw them doing this with the Steel Dragon. I couldn't believe it. They would run the coaster, and during calibrations, etc., they would be out there rubbing the tracks down in the valleys, and at specific points on the course. VERY strange. I am not saying that this is the reason for the walkways. I think it is a number of things....the Japanese are over the top when it comes to safety. Regardless, seeing this was a new experience for me. My wife, who is Japanese, thought it was so nice of them to think about our safety like that. HA!
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