The speed-range conundrum . Of course, the last item in that list is the great bone of contention. And it’s based on the item before it, building for the worst-case scenario. Many operators with hand braking courses would say that the worst-case scenario—in which all braking systems on the course fail—is highly unlikely. And they argue that limiting hand braking to speeds below 15 mph for the landing is needlessly restrictive. Nor is it easy to determine what the landing speed will be in all cases, making it difficult to determine when the 15-mph threshold will be met. Nonetheless, Klajnscek’s presentation retained the failed draft’s three-tier speed-and-braking system requirements. That approach specified: 1. No braking system is required for landings at 6 mph or slower. He allowed that this is not a hard and fast speed limit; a landing at 7 mph is not appreciably more perilous than one at 6 mph. 2. Between 6 mph and 15 mph, hand braking “can be” OK, in conjunction with guide and/or auto braking and an emergency brake. 3. Above 15 mph, no hand braking can be considered part of the actual braking system.
threshold for arrivals, and how to account for weather/ wind/weight extremes that make the arrival speed unpredictable. This discussion illustrated the practical difficulties of establishing rigid speed ranges, as the previous draft had included. It’s possible that a reasonable solution would be to require longer, gentler braking zones, not to outlaw hand braking or establish speed ranges that are problematic to determine in practice. That idea would seem to be worth adding to the discussion list. The fail-safe dilemma. Klajnscek also injected the idea of requiring “fail-safe” systems into the discussion. (The current ANSI/ACCT standard makes no mention of fail-safe systems, though the current ASTM standard does.) Fail-safe means that the entire system must stop the rider safely even if all the individual braking system components fail. That’s an extremely high bar. To clear it, the ASTM standards assume that the failure of two automatic systems used in sequence is so unlikely to fail that such a redundant system can be deemed “fail-safe.” (When is the worst-case scenario not the worst-case scenario? When we say so.) The Path Forward Despite any shortcomings, Klajnscek’s proposals serve as a starting point for drafting a second attempt at an
update to the current standard’s treatment of braking. It’s not the physics that is in dispute, it’s how to best brake participants given the experience they are seek- ing. Hand braking zip lines require the participation of the riders, and that makes the experience fundamen- tally different from a zip line with an auto braking system. That responsibility may be essential to the experience for some participant-directed recreational and educational operations. The notion that brake systems must be “fail-safe” does not come from the aerial adventure world, and it may not be appropriate to apply this standard to all zip lines. Given that some element of risk is acceptable in adventure and education and how problematic the idea of a “fail-safe” system is for aerial adventure and education, this should be a topic of discussion, not a given. ACCT is in the process of revising its accredited pro- cedures for producing its ANSI-approved standards. This process is likely months away from completion; it requires approval by two separate bodies, and a possible public comment period if ANSI considers the changes substantive.
There was some discussion during the session of whether 15 mph or 20 mph should be the top
Once new procedures are set, though, it will be up to all stakeholders to at least pay attention and/or get
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