How Zip Lines Work

Zip Line Safety

The first rule of zip line safety is to trust the professionals. While any kid with an elementary grasp of gravity and a pulley can make a zip line in his or her backyard, a professional accreditation by either the Professional Ropes Course Association (PRCA) or the Association for Challenge Course Technology (ACCT) ensures a regulated experience.

Both of these organizations are now accredited by the American National Standards Institute (ANSI) to develop industry standards and regulations. The European Ropes Course Association regulates zip lines in Europe, and accredits courses for safety. Some governments (Australia and Germany), as well as some U.S. states, regulate zip-line courses.

Steve Gustafson, president of the PRCA board of directors, says that when you're checking out a zip-line adventure, ask the operators about their accreditation with the PRCA or the ACCT, and their insurance policy -- commonly worth $1 million.

Now, let's get to the nitty gritty of what we're really all thinking about before we step into nothingness: What the heck is going to happen if the cable breaks? And keep in mind that 250 pounds (113 kilograms) is generally the weight limit for any one zip-line rider (depending on the company and particular zip line itself), lest you think that only waifs and sprites are gliding down a line.

As Gustafson points out, a cable "doesn't catastrophically fail overnight." He says that what we think of as one cable is actually seven smaller cables wound together, and each of those seven cables is actually made up of 19 even smaller cables. These smaller filaments show signs of wear before a line snaps suddenly, and staff members are expected to inspect lines daily for signs of wear.

Some companies will use two smaller cables with two pulleys. Gustafson argues that having two small cables -- not to mention twice the pulleys, the carabiners and other equipment -- increases the risk for both human error and unequal distribution on the ropes.

However, you don't have to immediately abandon your zip-line adventure if you're on a course with a double-cable system. Gustafson recommends you make sure to ask if the cables work together, as opposed to one being a "back-up."

Gustafson says to picture it like car tires; if the tires on the right-hand side have lower pressure than the tires on the left, the wear will be different. It's the same with ropes -- a balanced system makes a safer system.

Now that you've received safety instructions, consider yourself prepared to learn about some zip-line trips that have gone very, very wrong.