Braking News


The strengths and weaknesses of the ANSI/ACCT standards-development process were on full display at the ACCT annual conference in Oklahoma City this past February. Perhaps the most revealing session in this regard was “Zip Line Brake Systems & Landings, Part 2,” presented by Rich Klajnscek of Sea Fox Consulting. 

The session drew a large crowd, perhaps 75-80 persons, maybe more. It was a continuation of a session Klajnscek presented the previous year in Portland, Ore. Both sessions outlined the research and thinking that went into the development of the most recent ANSI/ACCT Draft Standard distributed in the fall of 2022. One key difference: some of that thinking had been rejected by the time this year’s session took place.

The draft standard was largely the work of a few individuals on the ACCT Technical Information, Research, and Education (TIRE) Committee, including Klajnscek, and the negative comments from the broader aerial adventure and challenge course industry showed that there was no consensus about this thinking. This was especially the case with the draft standard’s treatment of hand braking.

Despite that lack of consensus, Klajnscek’s presentation largely repeated the ideas and rules that the failed draft standard embodied. He appeared to believe that a few tweaks to the draft would be sufficient to win over those who had submitted negative comments, and that there was little room for changing the draft’s requirements regarding zip line braking.

Based on conversations API has had with designers, builders, and operators over the past year, as well as the parallel work being done by ASTM, it would appear that others will continue to disagree with Klajnscek and the TIRE Committee on that front.

That in itself demonstrates a shortcoming in the way the most recent draft standard was developed: too few individuals had contributed to it (a shortcoming ACCT is actively working to rectificy; see “Charting a New Course for Standards,” p. 10). There was little to no input from people who design, install, or operate hand braking systems. 

That input, though, will be essential to arrive at a draft standard capable of achieving future consensus. And it will likely lead to a standard that approaches braking, and hand braking, in a different manner.

Make no mistake, Klajnscek has the best of intentions. He is a respected and knowledgeable engineer with decades of experience in aerial activities. He invested a good deal of time and research into braking and, crucially—through his work as an inspector and an expert witness—into the causes of collisions between humans and between humans and objects.

Points of Agreement

A good portion of Klajnscek’s presentation focused on the physics involved in collisions—not just on zip lines, but collisions between people and objects in general. He explained the widely accepted idea that impacts between people and objects become significant and increasingly severe as speeds exceed 15 mph (as was outlined in an ACCT advisory in 2022 that Klajnscek helped draft). As such, the speed-risk relationship should inform how we look at speed on zips, he said.

The standard, he argued, must address preventing collisions with people or “stuff,” the appropriate brake for the landing speeds, preventing rider interaction when that’s too risky, braking riders gently, and consider worst-case scenarios. Most people would agree with those points.

But there’s far less agreement on how to achieve these goals.

Points of Disagreement

Klajnscek makes several assumptions that are clearly not shared by others in the industry, including many who have more experience in hand braking design, installation, and operations.

For example, Klajnscek noted that in his experience as an expert witness in court cases, 75 percent involved zip line incidents, and 59 percent of those (44 percent of all his cases), involve brakes/landings. His expert witness work, though, is not representative of all incidents involving zip line operations, nor is it representative of the operations and experiences themselves, commercial or educational. Nor was hand braking involved in all the brake/landing lawsuits. (To the contrary: Insurance claims data indicate that most lawsuits around collisions during braking involve automated systems, not hand braking. See “Analyzing 2023 Incident Trends,” p. 16.)

Klajnscek stated that collisions with objects are relatively rare, a point on which many in the industry agree. However, collisions with people, he said, are “still common”—a characterization that many North American operators would likely reject, even if collisions with people occur more often than collisions with objects. Plus, many of the collisions involving people that end up in court occur on zip lines with automatic brakes; the main issue in these cases surrounds communication between the sending and arrival platforms, not the type of brake used.

Simply put: Klajnscek (along with some other members of the TIRE Committee) believe that guests and even guides are unreliable when it comes to hand braking, and that automated systems are much more reliable. Operators, designers, and builders of hand braking zip lines believe that guests are in fact quite capable of hand braking, guides are even more so, and that automated systems are less reliable, efficient, and gentle in practice than the engineers believe. And, again, it appears that many collisions between people are the result of communication breakdowns between sending and arrival platforms, regardless of the braking system used.

Discussion Items

Klajnscek listed several items that he feels should be “on the table” for discussion during development of the next draft standard. These include:

  • Departure control systems, to prevent launch before line is clear.
  • Self-guided zips should require instructional signage.
  • Padding on platforms and use of e-brakes when contact is possible.
  • During testing, analyze what happens when participants don’t brake.
  • Being ready for people to fail to brake.
  • Building for the worst-case scenario.
  • Requiring the use of passive primary brakes (automatic brakes) above 15 mph.

The first five of these points seem eminently reasonable. They are common-sense steps that address guest safety. At one point in the session, Klajnscek noted that departure control systems become more critical as zip lines get longer and it becomes more difficult for a guide at the launch point to assess whether the line is clear. Again, it’s hard to argue with that; many of these points have been addressed in the PRCA and ASTM standards already.

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: 

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.

Between 6 mph and 15 mph, hand braking “can be” OK, in conjunction with guide and/or auto braking and an emergency brake.

Above 15 mph, no hand braking can be considered part of the actual braking system.

There was some discussion during the session of whether 15 mph or 20 mph should be the top 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 seeking. Hand braking zip lines require the participation of the riders, and that makes the experience fundamentally 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 procedures 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.

Once new procedures are set, though, it will be up to all stakeholders to at least pay attention and/or get involved in drafting the next revision to ANSI/ACCT 03.2019. Everyone’s point of view matters. That’s the only way to achieve a consensus standard and avoid a repeat of the most recent failure.


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