Quantified Tree Risk Assessment

Our consultants are trained in applying QTRA assessment methods in order to determine the risk of harm, if any, posed by the trees on your property.

The QTRA Method

The Quantified Tree Risk Assessment system applies established and accepted risk management principles to tree safety management. Firstly, the targets upon which trees could fail are assessed and quantified, thus enabling tree managers to determine whether or not and to what degree of rigor a survey or inspection of the trees is required. Where necessary, the tree or branch is then considered in terms of both impact potential (size) and probability of failure. Values derived from the assessment of these three components are used to calculate the probability of significant harm occurring.

The system moves the management of tree safety away from labeling trees as either ‘safe’ or ‘unsafe’ and thereby away from requiring definitive judgments of either tree surveyors or tree managers. Instead, QTRA quantifies the risk of significant harm from tree failure in a way that enables tree managers to balance safety with tree values and operate to a predetermined limit of reasonable or acceptable risk.