Highlines provide more reach for your rescue ops

This track line was pretensioned with one person hauling on a 3:1 MA. Note the sag with the load on the system. The 3:1 MA per track line should result in the proper amount of sag for safe operations. However, tandem prusiks at the near side anchor’s pretension point provide a crucial tension release in the system should it become over-tensioned.

If you ask different rescue teams what they think about highlines, you’ll probably get a wide range of responses. Some rescuers think they’re great and practice with them frequently; others might laugh a little and tell you they have no use for them. But everyone agrees highlines are resource-intensive operations that demand the most from any rescue team.       

Highlines Defined

A highline is a rope rescue system that spans horizontally or diagonally from point to point and allows rescuers to move patients and equipment across the space below it. Highlines allow for horizontal movement, which allows rescuers to avoid obstacles and, in some cases, save a tremendous amount of time and effort they would have used to move the patient or equipment via more conventional means.

Although highlines provide numerous advantages in horizontal movement over difficult terrain, they also have a number of disadvantages. First, they require significantly more rope and equipment than a conventional high-angle lowering or raising operation. Second, they are more complex and time-intensive to set up and operate than a conventional rope rescue system. And third, highlines can generate much greater or even catastrophic forces.

But practicing highline operations can build team skills because they require a team’s combined skills, plans and coordinated efforts. Highline skills are considered rope rescue technician-level skills in both NFPA 1670 and NFPA 1006. In fact, anyone desiring to become a certified technical rescue technician, according to NFPA 1006, must be able to direct the set-up and operation of a rope rescue on a highline.

With those things in mind, I’ll put highlines into simple terms so that set-up and operation are easier for the rescue team that doesn’t have an advanced math and physics expert on hand (which includes most of us).

Highline Types & Components

Highlines are generally classified as either flat or sloping in regard to their point-to-point perspective. For example, a flat highline might span a deep canyon from cliff edge to cliff edge, while a sloping highline might span from the top of a building to a point on the ground away from its base.

Sloping highlines typically rig the far side anchor much lower than the near side anchor, which allows fast transfer of rescuers, supplies

This 10,000-lbf. digital dynamometer was placed at the far side anchor with a tandem prusik bypass. Track line pretension was recorded and the far side anchor crew monitored the tension throughout the training. Note the far side tag line is managed with tandem prusiks and prusik-minding pulley.

and patients over the difficult and dangerous terrain below the high anchor. A typical example would be to go from a high point in a building collapse or disaster site to a point beyond the rubble pile. Sloping highlines are more practical than flat highlines because their loads don’t generate as much force when the lines are tensioned.

The same tensioning rules should apply to both sloping highlines and flat highlines; you’ll just have a bit bigger safety margin with a sloping highline. It’s easy to become lax and not use a far side tag line for a sloping highline because gravity will take the load to the far anchor. But this is a mistake; you won’t have a belay if the track line fails.

The three main components of any highline system include very reliable anchors at each end of the highline, the highline rope itself (referred to as the track line) and tag lines, which are operated from each side to move the carriage pulley or pulleys across the rescue area. Important: Tag lines can also function as back-up belay lines should the track line fail.

Optional components are also nice to have, such as a high-directional tripod. A high-directional keeps the track line well above the edge of a cliff or other structure, which greatly facilitates loading the carriage and moving it across the rescue area. For training purposes, it’s also nice to have a dynamometer to measure the peak forces generated by the track line.

Highline Terminology The English Reeve allows the rescuer to be lowered in the middle of the span. Here, rescuers load a patient and prepare to raise the two-person load back up to the carriage. Carriage: a pulley that rides on the track line with a load suspended from it. The carriage also has tag lines attached to it to allow rescue teams to move it. English Reeve System: a rigging configuration that allows the load to be lowered or raised vertically at any point on the highline. This allows rescuers to reach areas that would otherwise be very difficult to access. Kootenay carriage: a specialized knot-passing pulley that has multiple rigging points and can ride on multiple track lines (see illustration, at bottom). Near side anchor: typically the anchor point that’s the primary operation point for the highline system (sometimes referred to as the control side). Far side anchor: the anchor point at the remote point of the highline system. Tag line: allows rescuers to move the carriage across the track line. Also referred to as a control line, a tag line can also function as a belay for the track line. Track line: the main tensioned line that carries the carriage pulley. They can be one-track lines or multiple-track lines to increase the strength of the system.

This tandem track line was pretensioned using the system illustrated on p. 135. One person hauling placed 250 lbs. of static pretension on the system. The ends of the track line were then tied off and clipped into the main anchor. Note: Over time, your track lines will stretch and sag will increase. You can retension your system, but don’t use more than one hauler.

System Forces

The track line, which allows horizontal or diagonal movement in a highline operation, supports the load, or those being rescued. However, the forces generated by the load that pull down on the middle of the track line, called vector angle forces, can be great enough, in some instances, to cause anchor failure and major system component failure.                        

Simply put, the tighter the track line is tensioned, the flatter it will be with the load on it, which results in a larger angle (see “Single Track Line Tensioning System” illustration, at bottom). For example, an angle of 120 degrees would put 100 percent of the load’s weight on each anchor. An angle of 150 degrees would put 200 percent of the load’s weight on each anchor. If the track line were tensioned so tight that it stayed perfectly flat with the load on it (which is virtually impossible to do), the angle would equal 180 degrees, and it would put approximately 750 percent of the load’s weight on the system and anchors.

With a normal working load on it, typical rescue rope stretches 2–4 percent (the working load for 1/2" rope = 600 lbs. of force, or lbf.). This means that when the load moves out to the middle of the track line, the rope will stretch and the track line will sag, producing a smaller angle and reduced forces on the track line and anchors.

This rescuer is ready to ride the carriage down the sloping highline. The rescuer has two points of contact to the system as a standard procedure. Note the hangers ready to deploy. Rescuers must mind the hangers and send them out one at a time, roughly 30 feet apart.

The trick is to know how much tension you can put on a track line so you can safely place a general-use load (600 lbf. or 2.6 kilonewtons, or kN) on it. Most rescuers prefer less sag or droop in the track line because the flatter the track line, the easier it is to move the load. For example, 20 feet of sag in a flat, 100' track line means you must lower the load to the middle of the track line and then pull it back up the other side. Another reason rescuers prefer a flatter track line: to clear obstacles. (That is, after all, the point of having the highline in the first place.) However, too much tension could create catastrophic failure of your system.

Determining Tension

There are a number of methods you can employ to determine how much tension to place on a track line, the most conservative being the 10 Percent Rule1. This rule states you don’t put any pretension on your track line; instead, you put a visible amount of sag into your track line equal to 10 percent of the total distance spanned for every 200 lbs. you plan to place on the track line. For example, a 200' highline that will carry two people (equal to 400 lbf.) must have 40 feet of sag before any load is placed on it. Once the load reaches the middle of the track line, the sag will increase to at least 50 feet, giving you about a 120-degree angle and keeping your safety margin within the 15:1 range, which is the ideal safety margin for rope rescue work.

Another method you can employ to determine highline pretension is the Rule of 18 for 1/2" Rope2 (or the Rule of 12 for 7/16" Rope). In the Rule of 18, the product of the number of people pulling and the mechanical advantage (MA) of the tensioning system should not exceed 18. For example, six people pulling on a 3:1 MA (6 x 3 = 18) would meet the Rule of 18. The Rule of 18 (and the Rule of 12) will yield a flatter track line but much higher forces than the 10 Percent Rule.

This twin track line system was doubled, 300' rope. The middle bight was wrapped around the far side bombproof anchor with a full-strenth tie-off. Note: Make sure you pad any sharp edged on your anchors.

This litter basket is rigged with a two-carriage system. An Arizona Vortex high-directional tripod is used to create a high point to elevate the track line and tag line above the edge. Note the use of prusiks to attach the tag line to the carriages without knots.

This A-frame is anchored in position by simply placing prusiks on either side of the A-frame. No other guying is required to keep this high point in position.

A third school of thought involves pretensioning your track line while only one person pulls on a 3:1 MA (standard pull; don’t dig in and pull your hardest). If you use multiple track lines, you should not exceed one person pulling on the equivalent of a 3:1 MA for each track line. The 3:1 MA method is a compromise between the conservative 10 Percent Rule and the Rule of 18. When pretensioning with a 3:1 MA and one hauler, you should see 10 feet of sag with the weight of one person on a 100' highline.

When using multiple track lines to achieve a flatter line, it’s most common to use two track lines (tandem track lines) since doing so doubles your safety margin in regard to force on the track lines. For example, if a two-person load were generating 1,000 lbf. on the system, there would actually be 500 lbs. on each of the track lines. However, if you need an extremely flat track line, you may want to use four track lines (quad track lines). But when using quad track lines (or tandem), you must tension them with a force-distributing MA system (see illustration, at bottom). The purpose of a force-distributing system is to apply equal tension at the beginning of the operation and maintain it. You could end up with a combined total MA of 12:1 for the quad track lines. In that case, one person would tension all the track lines at once.

The definitive method of determining track line tension is to place a dynamometer in the system to measure real-time forces from moment to moment. If you use highlines on a regular basis, it’s probably worth your while to invest in a digital dynamometer. You can purchase a basic, 10,000-lbf. capacity Dillon digital dynamometer for less than $1,000.

Belaying Highlines

The industry standard during highline operations is to configure the tag lines so they can function as a reliable belay for the load/rescuer should the main track line system catastrophically fail. You can accomplish this by employing tandem prusiks on each tag line. When the load leaves one side, it is lowered by means of a descent control device (DCD), such as the brake bar rack, with tandem prusiks extending beyond the rack (see illustration, at bottom). The tag line on the far side employs tandem prusiks as well, and a haul team hauls the tag line. For spans of 100 feet or greater, using tag line hangers to hang the tag lines from the track line minimizes sag and potential slack in the tag line should you need to use them as a belay.

A Little Highline History Like most rope rescue concepts, the rock climbing community originally developed the concept of rope highlines. Climbers often refer to a highline as a tyrolean traverse, which is a rope that spans a gap or chasm. Climbers used the tyrolean as a means to move from point to point across a chasm. The term “tyrolean traverse” most likely came about because the practice of highline movement was developed in the Tyrol region of Spain. Rescuers don’t use the same term because rescue highlines incorporate a much broader set of configurations and applications than the original tyrolean traverse concept. The term “telpher” is often associated with the concept of a highline, and it refers to the use of a small car suspended from an overhead cable. Again, the rescue community does not use this term as a descriptive term for highline systems, but it fits in a general way.  Highlines in general have probably been most widely used by the construction industry on large construction projects, such as dams, to transport equipment and raw materials to remote job sites.

Setting Up Highlines

This Kootenay carriage is rigged as an English Reeve with an optional belay line for the rescuer. With the optional belay, this system becomes difficult to manage since each tag line and belay must be maintained with minimum slack as the load is moved both horizontally and vertically.

When setting up any highline operation, you must have a minimum of 1,000 feet of rope and lots of extra hardware (unless you’re only spanning a 30' gap). If you plan to perform a highline operation that spans approximately 300 feet with tandem track lines (flat or sloping), you’ll need 2,000–3,000 feet of rope.

To begin, select your start and end points primarily for their totally bombproof anchors and secondly for their work areas and approach and departure pads. Ideally, you should park your vehicle close to the nearest side’s anchor point to help tote gear to the site. Also, look for natural high directionals in trees or structural members to make loading the highline easy and safe.

Next, send a team of at least five rescuers to the far side of the rescue area to set up a main anchor and tag line anchors. They will need at least a dozen carabiners and at least six prusik loops for the tag line and hangers.

The near side team can then begin laying out gear in a resource area and setting up the main anchor and belay anchors. If you use trees as high directionals, you’ll probably need a webbing anchor for the tensioning system, an anchor for the tag line and an anchor for a reeve line, if you use one. It will also help if the team leader diagrams the locations of all anchor points and the general design of the system.

  Finally, getting the lines across the rescue area gap is probably the most complicated part of the process. Ideally, you can shoot a messenger line across with some type of line thrower, but you can always hike it across and have the far side team pull it up. For flat highlines, you’ll need to pull your track lines across the gap and at least one additional line to serve as the far side tag line. For sloping highlines, just pull your lines down to the far side anchor point.

This English Reeve highline system was set up to allow a rescuer to move across an industrial site to an inaccessible spot to rescue a worker. The tandem track line was pretensioned with one person and the highest tension measured equaled 1,050 lbf. when the two-person load reached the middle of the span, which was equivalent to 520 lbf. on each track line.

Tensioning the Track Lines

Once your track line and far side tag line are set up, you can tension the track line according to you favorite method. You should attach the tensioning system to the track line with two 8-mm system prusiks (see illustration, at bottom). Once you’ve achieved proper tension, attach the end of the track line with a full-strength tie-off, or clip the ends into an anchor. Important: Leave a loop (two feet of slack, for example) of rope between the prusiks and the anchor. In the event the system becomes overloaded, the two prusiks will begin to slip at about 3,500 lbf. of tension. In effect, a prusik acts like a clutch that relieves tension in your system if it’s overloaded.

Once you’ve tensioned the track line and set the tag lines with tandem prusik belays, you’re ready to use your highline to move loads horizontally. You can even configure an English Reeve System, which allows you to lower and raise your load when it reaches the mid-point of the track line (see illustration, at bottom). However, you must coordinate your tag line tension to prevent slack in one of the tag lines, since they are your effective backups should something happen to your track line.

Conclusion

Highlines provide an excellent rope rescue system for very specific applications, and they can be excellent training tools for your team, but they are time and equipment-intensive to set up and operate. If highlines are one of your team’s standard capabilities, you must practice them frequently to acquire a very clear understanding of the forces that can be generated on your anchors and system components.

References

1, 2: Vines, T., Hudson, S. High-Angle Rescue Techniques, Third Edition. Mosby. St. Louis, Mo. 407 pages, 2004.

Highline Belaying Video There is an informative video on highline belaying available from Rigging for Rescue, a rescue training company out of Ouray, Colo., called “The What-If of Highline Failure…Is There a Back-Up?” by Kirk and Katie Mauthner. It’s not a how-to video, just a critical look at the possibilities of main track line failure that will open your eyes if you’re not currently using a reliable belay technique for your highlines. Cost: $39. Phone/fax: 970/325-4474.