Zip Line Braking Systems: Are You Building a Zipline? We Stop Zipliners, so you don't have to.

The zipline standards released new zipline braking requirements for 2023 that eliminate hand braking as an option. Correct! Currently, the standards require a 3:1 factor of safety (safety factor), but currently, the standards (ACCT/ANSI 2019 and ASTM F2959) require a primary and secondary brake or a fail-safe braking system. This 3:1 Safety Factor is not new; a Fail-Safe trolley and compression spring system was installed at the Park City Mountain Resort (PCMR) in 2002. PCMR has had zero-braking-related accidents in 22 years.
Our insurance increases suggest that the zipline industry is accident-prone. A 2022 prediction (15/100,000) doubles the 2016 accident rates (6-7/100,000). Spring 2023, Adventure Park Insider magazine.
In 2020 at the ACCT Virtual Expo, Granite Insurance, NC, said zipline accident rates for 2016 (6-7/100,000 zipliners), and over half were braking-related. Suggesting brake failures at the number one accident-causing factor. This year, Mr. Annas published a 2023 prediction (15 accidents per 100,000) for 2022 zipline accidents after the statute of limitations expires. I know over half are still braking-related because my zipline accident investigations support these findings.
Industry groups estimate more than four hundred commercial zip lines in the U.S. across 48 states (the exceptions being Michigan and North Dakota) that service more than seventy million rides annually. Accounting for the 2022 prediction, which is over 10,000 accidents.
The problem with today's zipline trolleys (two wheels) is momentum (p=mv). Petzl told me their tandem-speed pulley could be calculated at 95% gravity (9.3 m/s2). As engineers, we know everyone reaches the lowest point (vertex) of a zipline (catenary curve) at the same time (gravity is constant). Still, once zipliners go uphill-just after the vertex-the problems arise, and stopping a zipliner's mass (m) becomes the variable that can triple the participant’s momentum (p=mv) (e.g., 80-lbs v. 240-lbs riders). (Most braking accidents involve heavier zipliners.)
The standards should require zipliner arrival speed testing using the maximum and minimum weight requirements for the zipline course. And account for cold temperatures, which shorten zipline cables and raise the vertex (less stopping distance and angle) Also, Safety Managers, guides, and Third-party Inspectors should be testing arrival speeds when temperatures are the lowest throughout the zipline’s season. Monitoring how fast a zipliner arrives is crucial to reducing risks associated with zipline braking failures. Thermal expansion or contraction of steel zipline cables occurs daily.
(Arrival speeds are inconsistent for high and low weight zipliners. They are rarely the same for ziplines using two-wheeled trolleys.) Some companies have reported a 5-MPH variation between high- and low-test weights. The ACCT 2019 standards say anything over 5-MPH requires a stand-alone emergency brake or EAD (Emergency Arrest Device). Stand-alone E-brakes are not brakes that someone resets. A spring braking system is an example of a stand-alone EAD, and the 3:1 safety factor still applies.
What can ASTM do to cut zipline accidents in half? (Require E-brakes on every zipline, YES, because accidents can be reduced by 50%.)
--Troy
Michael "Troy" Richardson
435-272-2389
CEO of Momentum Engineering
www.zipsafe.org
www.ziplinebrakingsolutions.com