BMP - Tree Risk Assessment - 23

4. Assessing Targets, Sites, and Trees
The likelihood of a tree failure impacting a target is the combination of the
likelihood of tree failure and the likelihood of that failed tree or tree part impacting a target. These factors must be assessed individually, then combined
to determine the likelihood of failure and impact. Likelihood of failure and
impact is then combined with the consequences of the failure to categorize
risk. These assessments are performed while inspecting the targets that could
be affected if the tree failed, site characteristics that influence tree structural
stability, and tree structural condition.

Targets
In tree risk assessment, targets are people, property, or activities that
could be injured, damaged, or disrupted by a tree failure. Targets include
people, buildings, animals, power lines, infrastructure, vehicles, landscape structures, and other property that may be damaged or harmed by a
tree failure (Figure 3).
Areas near a tree that are often evaluated for the presence of targets include streets, parking areas, footpaths, and play areas. Although damage to
structures is possible, the bigger concern is the people who use them, even
if people are not present at the time of the evaluation. Normally an assessor
should not identify the sidewalk or road as a target, but should consider the
people who use the sidewalk or road. Another example is that when assessing
the risk of a tree failing in a parking area, the assessor should consider possible damage to cars that may be parked nearby, the frequency and intensity
of use of the area, and injury to people who drive the cars.
The most important situations to assess are locations where people are
frequently present, such as places with heavy pedestrian traffic. The greatest
potential for injury from tree failures occurs in places where many people
are unprotected. Examples are bus stops and well-treed city centers. This
is especially important in areas where people will congregate under trees
during storms.
Roadways are a commonly assessed target area. Possible consequences
of a tree falling across a road include: the tree striking a vehicle and possibly
injuring people inside, a moving vehicle running into the tree that has just
failed, crashes associated with rapid stopping or swerving to avoid the fallen
tree, and disruption of access to points further along the road. There are also
costs and inconvenience factors associated with closing the road during the
clean-up and remediation process.
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BMP - Tree Risk Assessment

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