Subject: Cable Median Barriers – Part 1 Topic: Cable Median Barrier Incident Considerations Objective: Responders shall develop procedures for operations at center median incidents when a vehicle is contacting or entangled in tensioned cables Task: The rescue...
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Because the steel cables are typically installed in continuous lengths of 1,000 feet, there will be metal turnbuckles somewhere on either side of your incident. A cable that is in the way may be able to be loosened at the turnbuckle on either side of the incident scene until enough slack is created that the cable can be moved sufficiently. This author recently worked at an incident where a jackknifed 18-wheeler was entangled in several of the tensioned cables. State DOT personnel who responded to the scene used large pipe wrenches to relax the turnbuckles enough to create slack in the cables, allowing the vehicle to be released.
High-tension cable barriers can withstand multiple vehicle strikes and still provide cross-over protection, but when the cables are cut, at least 1,000 feet of barrier is placed out of service until it can be replaced. Transportation departments charged with the responsibility of installing and maintaining these systems request that emergency responders avoid cutting the cable whenever possible. There is no clean way to splice the cables together once they are cut so an entire 1,000 feet of cable would have to be replaced. This is costly and ordering new cable sections could delay fixing the cable barrier in a timely manner.
When the cables are still obstructing your patient extrication pathway and these previous options have all been tried without success, cutting becomes the final choice. Before a tensioned cable is ever cut, there are a series of recommended protocols that need to be in place to make cutting a safe and effective operation. First, instead of cutting the cable itself, remember that 1,000-foot sections of cable are connected together, and tightened with metal turnbuckles. The first location to consider for cutting cable should be the center of a turnbuckle itself. This location keeps the cable itself intact and allows repairs to be done more quickly. Prior to cutting, releasing tension at the turnbuckle should be completed first.
Use extreme caution when cutting the cable or turnbuckle – especially when it is fully tensioned. If the cable has to be cut, the cut location for the saw or power cutter operator must be at a section of cable where the cables are parallel, not twisted or pulled out of alignment. It is critical that the cut location also be between two intact support posts to minimize cable movement as the cut occurs.
Once the cut location is determined, the incident safety officer can establish a hazard zone and clear it of all personnel. The rescuer cutting the cable will obviously be the only person near the cable. It is safest directly at the cut itself because the free ends will travel away from you, to your left and your right.
In 2007, the Washington State DOT conducted a series of cable-cutting demonstrations. When a circular saw cut a tensioned cable between two undamaged posts, the cable on each side of the cut location retracted straight back about 15 feet toward the posts in each direction. Remember, it is like cutting a rubber band that is stretched tight. DOT officials reported that there was no whipping of the cable, but there was significant unraveling of the wire strands as the rotating saw blade made the cut. They recommend that the rescuer doing the cutting be protected with heavy gloves.
To address the frayed-end challenge, three to four wraps of duct tape were made on each side of the cable being cut in the second DOT demonstration. The holding power of the tape resulted in no frayed or unraveled strands at all. DOT officials recommend that responders wrap tape securely on both sides of the cable at the cut location prior to making the cut.
The third cable-cutting demonstration conducted by the Washington State DOT was very interesting. This time, a power rescue cutter was used instead of the rotary saw. To simulate the need to cut cable at a location where the posts had been torn away by the collision, all support posts were removed from the immediate area. To simulate a scenario where the cable is stretched around a vehicle at the scene, a construction machine was used to pull the cable about 15 to 20 feet from the center of the median. The demonstration showed that there was none of the anticipated whipping action of the cable as it was cut even though it was stretched and pulled out of alignment.