In this article, Adventure & Obstacle Sports Expert, Ian Adamson, details the design, construction, operations, inspection, and maintenance of zip lines and their components, as well as common failure modes that can result in injuries.
Industry groups estimate there are more than 400 commercial zip lines in the U.S. across 48 states (the exceptions being Michigan and North Dakota) that service more than 70 million rides annually. For ziplines to be safe, they must adhere to stringent requirements and standards for proper design, engineering, construction, operation, and management.
It has been my experience that zip lines, when properly run in accordance with these standards, can be both exciting and safe. Zip lines vary from backyard “DIY” contraptions that can be as simple as a piece of fencing wire and a clothesline pulley, to engineered commercial assemblies utilizing a comprehensive electro-mechanical system containing cables, attachments, trollies, computer control systems, hydraulics, motors and sophisticated braking systems.
Ziplines are not federally regulated in the United States. In most states, the labor department oversees zip lines, while in FL and PA it is the Department of Agriculture. Approximately half of the states have oversight by agencies responsible for roller coasters or elevators. In Connecticut and Minnesota, the state fire marshal is responsible, and in Arizona, Virginia, and others there is no state oversight. In these cases, zip lines are subject to city and/or county regulations.
ANSI and ASTM are among the standards organizations which have specific requirements for the design, performance, inspection, operation, and training necessary for zip lines. Other groups which address zip line safety are The Association for Challenge Course Technology (ACCT), the Lifting Equipment Engineers Association, and European Standards (EN).
There is no public database for zip line accidents, injuries or fatalities, although news reports and academic/medical studies provide insight on the magnitude of the problem.
According to a 2015 study by the American Journal of Emergency Medicine, the number of zip line injuries in the United States reached 3,600 in 2012, 11.64 per 1 million population. This compares with 0.0127 / 1 million population for amusement park rides (2015). Reported injuries included broken bones (46%), bruises (15.2%), strains/sprains (15.1%), and concussions/closed head injuries (7%). Ohio State University researchers found that approximately 12%of zip line injuries resulted in hospitalization.
Between 2006 and 2016 there were 16 zip line fatalities reported in the United States, predominantly from falls (77%), material failures, collisions, and entanglements.
Standards do not specify how to design zip lines but rely on “standard engineering practice in compliance with this standard, applicable building codes, and legal requirements as established by applicable regulatory entities governing occupational safety” (ANSI-PRCA).
Commercial zip lines commonly utilize wooden poles secured with wire rope and steel bolts or are integrated into aerial adventure courses that use trees as the support structure. Large builds, those with zip lines longer than a few hundred feet, require steel and concrete structures. These may require engineering expertise on the geology, foundations, structures, operations and maintenance of the systems.
Regardless of the application and use of a zip line, there are common issues which need to be addressed to promote safety. Selection of the site, geology, topography, historical weather conditions, construction materials, supports, and corridor clearances should be considered. The use of trees requires inspection from a qualified arborist to assess the health and vitality of the trees. Utility poles can provide flexibility in course layout and design but require relatively high maintenance and inspection compared to steel/concrete builds. The zip line corridor must be free of obstructions and requires daily inspection and routine maintenance to keep tree growth at a safe distance.
The wire rope (cable) and associated hardware requires daily inspection and routine maintenance. Inspection should involve assessment of components such as:
Participants in zip line activities are not responsible for the inspection of the system’s hardware and safety devices, however they may be able to evaluate the condition of the safety equipment. Potential causes for concern include safety equipment that appears tattered and worn or if the only braking mechanism provided is a heavy glove used to squeeze the cable. Crushed fingers, broken hands, and collisions with trees or supports can result from using this braking system.
Operator error is the predominant cause of zip line equipment failure and injuries. Common mistakes include sending a rider before the line has cleared downstream, resetting brakes improperly, failure to check harnesses and attachments, and miscommunication between the zip line operators. Inadequate rescue procedures and a lack of operator knowledge and experience and capabilities have contributed to injuries and fatalities, emphasizing the need for operators to undergo thorough training.
Personal Safety Equipment requires daily inspection by the zip line operator. This equipment can include helmets, harnesses, lanyards, carabineers, pulleys, and trolleys. Many injuries and incidents can be attributed to the failure to retire worn safety equipment and hardware. Operational procedures that require routine inspection and replacement of worn safety equipment can prevent these incidents.
Helmets should be inspected for fractures and proper operation of suspension and fastening systems. Harness inspections identify abrasions, stiffness, worn or broken stitching, ensure buckles operate properly, and that webbing does not interfere with buckle operation. Carabiners should be inspected for significant scoring, wear, cracks and distortion. Smooth operation of the gate and locking system should be verified. All moving parts on zip line trolleys should operate smoothly and they should be free of significant scoring, wear, cracks and deformation.
The Sports and Recreation experts at Robson Forensic are qualified to thoroughly examine whether the standard of care for obstacle courses was met in a situation where an injury has occurred. For more information, please submit an inquiry.