Tree risk is assessed by combining which two factors?
- The likelihood of an event and its consequences
- The species of the tree and the season of the year
- The age of the tree and the cost of removing it
- The height of the tree and the diameter of its trunk
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A. The likelihood of an event and its consequences
Risk combines how likely it is that a tree or part will fail and strike a target with how severe the consequences would be. Size and species influence those factors but are not risk in themselves.
Reference: ISA Tree Risk Assessment Best Management Practices
A walk-by or drive-by inspection of a population of street trees, looking for obvious defects, is which level of assessment?
- Level 2, basic
- Level 1, limited visual
- Level 3, advanced
- Level 4, comprehensive
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B. Level 1, limited visual
A limited visual assessment views trees from one perspective to find obvious, high-priority problems across many trees. A basic assessment is a 360 degree ground inspection of an individual tree. There is no Level 4.
Reference: ISA Tree Risk Assessment Best Management Practices (levels of assessment)
In the standard qualitative method, which set of terms rates the likelihood of failure?
- Improbable, possible, probable, imminent
- Low, moderate, high, extreme
- Very low, low, medium, high
- Negligible, minor, significant, severe
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A. Improbable, possible, probable, imminent
Likelihood of failure is rated improbable, possible, probable or imminent. Negligible to severe rates consequences, very low to high rates likelihood of impact, and low to extreme are the final risk ratings.
Reference: ISA Tree Risk Assessment Best Management Practices (risk categorization)