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Zip-Line Slides and Horizontal Gliders
Zip-line slides, also called cable-trolley rides, are simple, inexpensive-to-install pieces of playground apparatus that are found in many recreational environments. Historically they have been located mostly in a more isolated camp setting, but they are now often found in a county or municipal park, on a school playground, and even on YMCA premises, sometimes in the more sophisticated form of a horizontal glider. These minimal pieces of equipment offer an enormous amount of potential fun. They also offer an equally enormous amount of probable injury. Frequent and often severe injuries result: some arise from physical defects, more from user incompatibility, but most result from inadequate supervision.
A zip-line's most common use is as an adventure or thrill ride, but they are also used as an entry device for swimming holes in lakes, ponds, or rivers. Thus, their ride paths and termini may vary significantly. They also differ in type, most being simple "hang on and drop" devices. Some, however, have seats or stands and the rider stays on the device until it is (basically) motionless before disembarking. The height above the ground at the end position also may differ significantly on "home-made" systems.
The following list depicts the four avenues of potential loss that must be thoroughly considered and adequately addressed to provide an acceptable zip-line experience. All are important, but laxness in the area of supervision will completely negate even stellar work in all the others.
Design: adequate consideration and selection of the site and physical components;
Installation: proper and substantial cable anchoring and resilient surface preparation;
Maintenance: documented, regular, and responsive; includes documented inspections
Supervision: ownership, operation, participants, monitoring;
The following basic physical components and potential defects are part of the safety equation in each of the first three aspects of zip-line safety.
| Components: |
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cable (steel wire rope) or rail (rigid metal pipe, bar, or channel) with a slight downward slant from the starting to the ending point; hereafter called "cable";
supports at each end of the cable that are capable of holding the assembly's total dynamic force when used to capacity; this can be a single post, a pair of posts joined by a beam, an arch, a tree, a building, etc. at each end;
anchor connections at each end of the cable to secure the cable to the support;
an elevated starting platform (or terrain such that the slope of the ground from the starting point to the ending point is greater than that of the cable);
a carriage consisting of a carrier assembly with at least 1 roller that allows movement along the cable from the starting point to the ending point;
a handle, standing peg, or seat on which the rider hangs, stands, or sits while riding; the norm is a handle from which the rider drops to the ground;
a termination block to stop the forward progress of the carriage and end the ride; sometimes the cable is strung so that an arc describes its path instead of a line... in such cases, if there is enough difference both vertically and horizontally between the low point and the end point of the cable, a block is unnecessary, as the obtainable momentum is insufficient for a rider to reach the cable's end;
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| Potential defects |
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supports
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improperly installed post, posts, or arch; vertical member not deep enough in the ground, not set in concrete, and/or not adequately braced;
inadequate mass or holding potential of other support to sustain the forces contemplated, e.g., too small a structure, too small a tree, etc.;
inappropriate condition of support, e.g., damaged post, unhealthy tree or root system, deteriorated structure, unstable ground around the post, etc.
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anchor connections:
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inadequate material, size, or strength rating for the forces and elements contemplated;
mounted in such a way that normal flexing of the system will either
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- allow the anchor connection to work free;
- cause damage to the support or anchor point;
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situated so that they may cause injury to participants;
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cable and cable installation:
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insufficient strength rating for the potential load;
inadequately anchored or connected;
too high above the ground; norm is approximately 72" above grade
excessive slope on the cable from starting to ending positions;
inadequate cable arc to ensure self-stopping (i.e., low point of cable arc not low enough with respect to end point to prevent riding to cable end) ;
inadequate cable end position to ensure self-stopping (i.e., cable end not far enough from the low point of the cable arc to prevent riding to cable end);
cable is frayed or otherwise damaged;
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carriage:
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accessible to participant (from ground, handle, peg, or seat);
inadequately guarded roller(s);
loose assembly or mounting bolts;
worn or defective roller(s);
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handle, peg, or seat:
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peg or seat is of a design that allows or encourages the rider to jump off rather than disembark after the motion has ceased; (note: handles are designed for dropping off while the ride is in motion);
handle, peg, or seat is insufficiently attached (by design or by wear);
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starting point of the ride:
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starting platform is excessively elevated (i.e., is so high a fall would cause injury)
starting platform has inadequate guarding (i.e., is high enough that it warrants a restricting barrier around its perimeter that is not so provided);
starting platform has inadequate access (i.e., is high enough that ladder or steps should be provided and are not, or that steps are provided, but they are of a height that warrants a hand rail that is not provided);
starting platform allows participant access to the carriage;
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termination block:
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missing (and required by design of the cable installation);
loose or otherwise insufficiently attached;
too close to support, allowing participant to strike support;
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fall zone:
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fall zone dimensions are inadequately defined, i.e., the fall zone:
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- does not begin 6' before the starting point,
- does not extend at least 6' to each side of the cable's pathway, or the footprint of the support if double posts or arches are used;
- does not extend past the end point as far as a person could reasonably be expected to land (i.e., probably more than 6');
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fall zone is not protected by fall absorption material (i.e., bare dirt, grass, hard-paved surface, etc. is found in the fall zone);
fall absorption material of an unsatisfactory type is provided
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- unacceptable include:
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:: sand;
:: wood chips or compacted wood shavings
:: dirt commingled with wood chips or round aggregate
:: crushed rock or similar products;
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- acceptable include:
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:: engineered hardwood fiber;
:: non-compacted wood fiber or shavings
:: shredded tires,
:: clean round aggregate (1/4" or 3/8" with no sand)
:: engineered composition mat or similar product;
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fall absorption material is of insufficient depth for the type:
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minimum acceptable is 12" depth of non-compacted wood shavings or shredded tires
may be less for engineered hardwood chips or engineered composition mats, etc. (see manufacturers' guidelines);
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| Maintenance: |
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annual documented inspections (with documentation saved at least 3 years) should be made of:
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cable and anchor connections;
carriage assembly;
fall zone protection;
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daily inspections should be made of:
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starting platform (not wet, not icy, proper access, etc.)
carriage assembly (moves freely, properly riding on cable, inaccessible to participants)
handle, peg, or seat (not wet, adequately secure, etc.)
fall zone protection (no foreign material, loose protective material sufficiently spread, etc.)
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preventative maintenance (documented annual check of all moving and structural components)
responsive maintenance (documented verification of inspection corrections)
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As noted above, supervision or lack thereof, presents the largest potential for loss from these pieces of equipment. The loss can arise from ownership, use, improperly qualified participants, or inadequate monitoring, as noted below.
| Ownership: |
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attractive nuisance hazard: "if it is there, they will come;" such an attraction creates liability, even if it is in a remote location or behind a locked fence; its very presence will probably make any injury affix to the owner (or a corporate user, i.e., an entity who allows children to use the equipment as part of their program or use of the general area) as the child is not old enough to assume the risk of use;
installation: deficiencies of construction, such as noted in the above sections, will haunt any defense because of the age of the victim; the only possible reprieve might come from use by a corporate user, and then probably only with an appropriately drafted use agreement;
maintenance: deficiencies of maintenance and inspection, as noted in the above sections will similarly haunt any defense, again reprieved only by a corporate user and a favorable use agreement;
use agreements: a properly worded agreement can be used to contractually shift complete responsibility to a corporate user (at least as long as they are the entity controlling the equipment or playground); lack of any such contract between owner and corporate user will leave the owner probably liable for attractive nuisance related losses and possibly liable for losses attributed to installation and maintenance.
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| Use: |
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use agreements: such a document that favors the property owner instead of the corporate user (e.g., a YMCA who uses a school grounds for after-school care) can make the corporate user responsible for the owner's deficiencies; a neutral document could specify that the owner is responsible for injury arising from inadequate construction or maintenance;
inspections: even with a neutral or positive use agreement, a corporate user will probably be held liable for lacking or insufficient inspections, especially of the daily variety, as they are the last responsible party to view the equipment;
maintenance: unless the use agreement is very owner-favorable, this arena is not the responsibility of the corporate user, but the results of inadequate maintenance may still be accrued to the corporate user because of the responsibility to inspect;
local condition response: this responsibility is an extension of inspections, but references not innate physical equipment defects but temporary ones caused by weather (wet or icy equipment, etc.) or other factors (drop-zone insufficiency caused by shifted resilient material, tree limbs, animal excrement, etc.)
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| Participants: |
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individually appropriate with regard to
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age: zip-lines are virtually inappropriate for <5 year olds, and only for 5-12 year-olds under certain construction and physical size conditions;
size: even age-appropriate children may be too small for the equipment, if their stature will cause too great a distance for a safe drop to the ground.
physical condition: even appropriately sized, age-appropriate children may not have sufficient strength to safely ride some of the longer devices to the end, or may not be resilient enough to safely drop to the ground at the ride's termination;
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appropriate numbers: completely qualified children may be so numerous or so active that supervision by any number of staff is inadequate;
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| Monitoring: |
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supervision by staff
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qualified personnel: staff supervising the play area should be certified in first aid and CPR;
adequate number on duty: minimum ratios as required by licensing or by internal standards should never be violated; this is a type of activity that should require supervision above minimum ratios; if staffing is not available, the equipment should be off-limits to the children;
proper positioning with regard to equipment: staff needs to be properly situated with regard to the activity, i.e., one near the start to supervise and assist children getting on the device and another one near the end to oversee dismounts and to keep the area clear of other children; if the length is sufficient, another should be stationed in the middle;
attentive demeanor: all staff assigned to this equipment should be actively monitoring it when it is in use; as can be surmised, the equipment demands significant supervision;
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no unsupervised use permitted: strict enforcement with mandatory discipline should be employed; to permit access is to embrace liability;
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Most reported injuries arising from zip-lines are significant, with the most frequent being a fractured bone. By far the most frequent cause of injury is inadequate monitoring, often exacerbated by the age inappropriateness of the victim. Since participant usage is controlled (or not controlled) actively or passively by the staff and management, that whole sector is actually monitoring also.
Zip lines are relatively inexpensive pieces of equipment to install: their expense is operational (from staff time expended for maintenance and monitoring) and consequential (from pain and suffering experienced, and dollars spent because of injuries). A commercially fabricated and professionally installed horizontal glider reduces some of the exposure by a more controlled environment (i.e., a shorter drop, shorter ride, more protected carriage, etc.). Such a unit also transfers some of the exposure, as the liability for design, manufacture, and installation belongs to the manufacturer and installer, not the owner, assuming they will be accessible at the time of an incident. The bottom line, however, is that any of these units should be carefully considered before installation.
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