10.2 Targets and Occupancy

Finding What Could Be Struck

A target is anything of value that could be struck if a tree or tree part fails. Targets include people, homes, vehicles, roads, trails, benches, playgrounds, utilities, fences, signs, outdoor dining, and work zones. In exam scenarios, target analysis frequently changes the best answer: the visible defect may be identical, but the risk concern shifts when the target shifts.

Occupancy is the pattern of target presence within the strike zone over time. The ISA Basic Tree Risk Assessment Form grades occupancy rate on a four-step scale, and the same scale is worth memorizing for the exam:

Higher occupancy raises the likelihood of impact in Matrix 1 and can raise the consequences in Matrix 2. A sidewalk outside a school at dismissal has frequent-to-constant occupancy; a remote trail used once a month is rare. A patio may be seasonal; a parking lot may be full by day and empty at night. Always ask how the area is used, when, and whether use could change.

Target Management as Mitigation

Target management reduces exposure without altering the tree. Moving a bench from under dead branches lowers occupancy immediately. Closing a trail during storms lowers occupancy during high load. Redirecting pedestrian flow buys time until pruning is scheduled. Exam answers that focus only on the tree are not automatically correct — a target solution can be the best answer when it effectively reduces exposure and is practical.

Avoid assuming an area is unused without evidence. A vacant lot may be a children's shortcut to school; a quiet courtyard may host events; a maintenance road may carry daily workers. Good target analysis asks the owner, reads site cues such as worn paths, and records assumptions.

Target Analysis Questions

1. What person, property, activity, or infrastructure is within striking distance?
2. What is the occupancy rate: rare, occasional, frequent, or constant?
3. Is presence predictable by time of day, season, weather, or event schedule?
4. Can the target be moved, restricted, shielded, or redirected?
5. Would use change if the site is redeveloped, opened, or staffed by workers?
6. Are emergency access, utilities, or transportation corridors involved?

Scenario: A broken limb is suspended over a picnic table. If the table can be moved today, relocating it cuts occupancy while pruning is scheduled. If the table is anchored and used daily, prompt pruning or access restriction becomes urgent. The target decision sets the timeline.

Scenario: A cracked limb extends over a road. The target set includes not only vehicles but pedestrians, cyclists, emergency responders, and property beyond the curb. With frequent occupancy and serious consequences, the arborist should communicate urgency and may restrict the area until mitigation is complete.

Target analysis also drives reinspection intervals. A known defect near a frequent-occupancy playground should not wait long for reassessment, and a low-use area that becomes a festival site invalidates the old assumptions. For the exam, never skip the target: risk requires the combination of potential failure, target, and consequence, and the best answer often identifies the target first.

Target Zone, Direction of Failure, and Multiple Targets

The target zone is the area a failed part could reach, not simply the ground directly beneath the defect. A leaning stem may fall well to one side; a long, heavy limb can swing or telescope on impact and strike farther than its drip line. When you map the target zone, account for the likely direction of failure — toward a lean, downwind for a wind-load failure, or downslope on unstable ground — because likelihood of impact rises sharply when the probable failure direction points straight at an occupied target and falls when the target sits outside the swing.

Many scenarios involve multiple targets of different value and occupancy inside one zone. A single defective stem over a corner lot might overhang a constant-occupancy house, a frequent-occupancy sidewalk, and a rare-occupancy alley at once. The ISA approach is to assess each target separately and let the highest combination of occupancy and consequence drive the recommendation and urgency. Recording every target also protects the assessment when use shifts: if the sidewalk later becomes a bus stop, the documented occupancy change makes the case for reassessment obvious.

Finally, distinguish a target's occupancy from its value. A constantly parked but inexpensive shed has high occupancy yet modest consequence, whereas a child's play structure used only on summer afternoons has lower occupancy but severe consequence if struck while in use. Strong exam answers weigh both dimensions rather than treating any single occupied object as automatically decisive.