Technical Tree Falling – Faller Escape Routes, Understanding the 5-15-90 Rule (Article 4)
By Dwayne Neustaeter
Having a clearly identified and prepared escape route is one of the most important parts of any felling plan. Statistics show that a well-planned and utilized escape plan has a significant impact on your personal safety. Accident and fatality reports also reveal some useful information regarding workers injured when falling trees.
People falling trees have learned over the years that the area directly on either side or directly behind the tree is very dangerous. This is because branches, tops and trunk sections often fall near the base of a falling tree.
One type of falling mishap, know as a barber chair, is particularly dangerous. A barber chair occurs when a tree being felled delaminates vertically before the hinge is cut thin enough to bend. The term refers to the sliding action of the old style barber chair that positioned patrons in a head down, feet up position so the barber could more easily shave with the straight razor.
In falling, a barber chair occurs when using conventional back-cuts where the hinge is formed by cutting the wood from the back of the tree towards the hinge. As the saw severs the more resilient sapwood fibres typically found in the outer rings of a tree, the more brittle heartwood must resist the bending load. In cases of heavy forward lean and in older trees, this can result in the hinge wood splitting upwards as the tree falls. When the tree top contacts the ground the section of tree that has split upwards crushes either the remaining wood column straight backwards or the split standing section tears and rolls off to either side. In either case, the best place to be is away and at an angle.
Another compelling justification for the escape route is that while a tree is being cut, vibrations sent up through the entire tree can cause branches and tops to loosen. This vibration dislodges branches, where the sway from wind will not. As a tree begins to fall the force of gravity acting on it changes as well and a branch or dead top that is hung up for many years will suddenly dislodge during the first several seconds the tree is falling. These loosened limbs and tops fall generally within a few feet of the base. Trees that have dead tops or dead branches often referred to as widow makers for this very reason, because many a tree faller has been struck or killed.
The 5-15-90 rule is a concept we can use to emphasize the importance of using an escape route. Review of where tree falling accidents and fatalities occurred revealed that 90% of all accidents and fatalities happen within the first 15 seconds of the tree falling and within 5 feet of the base of the felled tree. Therefore, if you identify, plan and use an escape route you can increase your chance of survival or escaping injury by 90% and that the best escape route is at an angle away from the falling tree.
The most advisable angle of escape is away from the direction of the falling tree at an angle approximately 135 degrees from the direction of fall or 45 degrees from the opposite of the direction of fall. (see diagram)
Many times obstacles or terrain influence the escape route plan, therefore it is not an exact science but rather the escape zone is at an angle diagonally away from the direction of fall, as illustrated in the diagram.
Remember: Identify, Prepare and Use an Escape whenever you fall a tree.