We have just added QTRA to the list – we are keen to get your feedback and suggestions for improvements.

OTISS now supports various tree safety risk assessment methodologies. As part of each tree inspection, you fill in the risk factors and these are used to automatically calculate a resulting risk category. OTISS supports the standard methodologies listed below, and you can also adapt the two configurable algorithms to setup your own method.

  • ISA Tree Risk Assessment (2013) – International Society of Arboriculture
  • QTRA (V5.1) – Quantified Tree Risk Assessment Method as described at www.qtra.co.uk.
  • THREATS – Tree Hazard: Risk Evaluation and Treatment System
  • Matheny and Clark (1994)  Tree Risk Assessment
  • BASIC Tree Safety Inspection
  • Configurable addition based methodology
  • Configurable multiplication / probability methodology
  • CAVAT – we are investigating how this may be included in a future release.

See below for more details.

ISA Tree Risk Assessment (2013)

On the TreeSafety Customise Survey webpage, use the Survey Templates button to select the ISA methodology. This will setup the OTISS fields to match (as far as we can) the ISA Tree Risk Assessment Form (Level 2) and terminology described at http://www.isa-arbor.com/education/onlineresources/basictreeriskassessmentform.aspx  (Copyright ©2013 International Society of Arboriculture). It is expected that you will adapt these configurations for your specific needs.

TreeSafety ISA matrix

The Risk Categorisation section is done for the whole tree and uses the OTISS risk assessment fields to automatically calculate the overall Risk Rating. During a survey, when you enter (or change) the Likelihood of Failure and the Likehihood of Impacting Target fields, then the Failure x Impact field is automatically calculated. When you then enter (or change) the Consequence of Failure field, the Risk Rating iscalculated. The ISA matrixes shown above are used for all calculations, and the two calculated fields are visible but are configured as read-only. NB: changing the configuration of any of the risk assessment fields may invalidate the ISA calculation method.

QTRA – Quantified Tree Risk Assessment Method

QTRA Risk calculation

On the TreeSafety Customise Survey webpage, use the Survey Templates button to select the QTRA methodology.  This will setup the OTISS risk assessment fields with the appropriate names and scores for Target Range, Size, Possibility of Failure and Risk of Harm. During a survey, when you enter (or change) any of these fields, then the Risk of Harm field is automatically calculated and colour coded using the QTRA V5.1 rules – the resulting RoH field is read-only.   NB: changing the configuration of any of the risk assessment fields may invalidate the QTRA calculation method.

A complete set of dropdown lists have been provided for the Target Range and in particular all the Vehicle options. Depending on the way you like to work, you may wish to reduce this list to a more manageable set of options. Simply go to the Customise Survey webpage, edit the Target Range field and delete the options that you don’t use. NB: changing the configuration of any of the remaining options may invalidate the QTRA calculation method.

The QTRA feature is only available to registered QTRA users. To activate these features, please enter the registration number from your QTRA certificate on your Account Settings page – we will check it at www.qtra.co.uk.

THREATS – Tree Hazard: Risk Evaluation and Treatment SystemTreeSafety THREATS customfield

On the TreeSafety Customise Survey webpage, use the Survey Templates button to select the THREATS methodology. This will setup the OTISS fields to match (as far as we can) the THREATS form and terminology described in the THREATS documents and spreadsheet at http://www.flac.uk.com/wp-content/uploads/2010/07/THREATS-GN-June-2010.pdf. It is expected that you will adapt these field configurations for your specific needs.

This will also setup three of the OTISS risk assessment fields with the appropriate names and scores for Failure Score, Target Score and Impact Score. During a survey, when you enter (or change) any of these fields, then the Risk Score field is automatically calculated by multiplying the three numbers, and the corresponding Threat Category is selected.  The two calculated fields are visible but are configured as read-only.  NB: changing the configuration of any of the risk assessment fields may invalidate the THREATS calculation method.

THREATS is intended for use by suitably qualified persons who have been trained in its use. Julian Forbes-Laird and Forbes-Laird Arboricultural Consultancy Ltd accept no responsibility for the use of THREATS or any outcomes resulting therefrom by untrained users. Any modification to the terminology and scoring systems within the method renders it inoperable and prevents it from being known as or referred to as THREATS.

Matheny and Clark (1994)  Tree Risk AssessmentTreeSafety Matheny survey

On the TreeSafety Customise Survey webpage, use the Survey Templates button to select the Matheny&Clark methodology.  This will setup three of the OTISS risk assessment fields with the appropriate names and scores for Failure Potential, Size of Part and Target Rating. During a survey, when you enter (or change) any of these fields, then the Hazard Rating field is automatically calculated by adding the three numbers (values 3..12), and the corresponding Hazard Category is selected.  The two calculated fields are visible but are configured as read-only.   NB: changing the configuration of any of the risk assessment fields may invalidate the Matheny&Clark calculation method.

This template will setup the remaining OTISS fields to match the ISA Tree Risk Assessment Form as described above. It is expected that you will adapt these configurations for your specific needs.

 

Addition(3) method

TreeSafety Add3 surveyOn the TreeSafety Customise Survey webpage, use the Survey Templates button to select the Addition methodology. This will setup the OTISS risk assessment fields with an example of an addition-based risk methodology. The remaining OTISS fields match the ISA Tree Risk Assessment Form as described above. It is expected that you will adapt these configurations for your specific needs.

Method Summary:  Allow the user to enter 1, 2 or 3 riskFactor values which are then added together. This number is then used to select a category from a set of ranges. During a survey, when you enter (or change) any of three risk factor fields, then the riskFactor4 field is automatically calculated by adding the three numbers, and the corresponding riskCategory is selected.

  • The riskFactor1, riskFactor2 and riskFactor3 are setup with some suggested names and scores for risk factors. The options for the dropdown list can either be the numbers themselves or can consist of a visible label and a hidden value – in the format ‘label=X’ . For example
3 ‘3’ is shown as one of the options on the survey form and 3 is the value for the calculation
High=5 ‘High’ is shown as one of the options on the survey form and 5 is the value for the calculation
Low(1)=1 ‘Low(1)’ is shown as one of the options on the survey form and 1 is the value for the calculation
  • The three riskFactor fields are configured initially as forceSelection. This means that only the options listed are allows. But you can change this if required.
  • If you hide one of these fields then it will not be part of the calculation.
  • The riskFactor4 is where the result of the addition will be shown.
  • The riskCategory is where the result of the addition is used to select a category. The options should be a list of categories and each option is of the format ‘label=X’ where X is the lower end of the numeric range for that category. The highest numbers must come first in the list. The lowest value should be the second to last options and the value should be zero. The last line of the riskCategory options is where OTISS is told what calculation method to use – you must always have this option.
 Severe(20)=20
Ten And Above(10)=10
Eight and Above(8)=8
Six and Above(6)=6
Lowest=0
*ADD3*  calculation
20 and above
From 10 to 19
from 8 to 9
from 6 to 7
from 0 to 5
*ADD3*  calculation
  • The two calculated fields are configured initially as read-only.

It is expected that you will adapt all of these risk assessment configurations for your specific needs. If you have difficulty configuring the risk assessment to do what you want, please call or email our support team.

 

Multiplication(3) method

On the TreeSafety Customise Survey webpage, use the Survey Templates button to select the Multiply methodology. This is similar to the Addition method described above except that the riskFactors are multiplied together (rather than added).

This method is suitable for multiplying 2 or 3 simple numbers, e.g. 3 * 4 *1 , but can also be used for probabilities. Probabilities are shown as decimal numbers: ‘1 in 1000’ is 0.001, and ‘1 in a million’ is 0.000001.

  • Example riskFactorN options and riskCategory configuration for probability based method – see notes above.

TreeSafety MULT3 customfield2TreeSafety MULT3 customfield

 

BASIC Tree Safety Inspection

On the TreeSafety Customise Survey webpage, use the Survey Templates button to select the BASIC methodology. This will setup the OTISS fields to match a generic Basic Tree Safety Inspection that would be carried out by an person without formal arboricultural qualifications (e.g. estate manager), but who has attended a Basic Tree Safety Inspection course and has appropriate experience. The risk assessment fields have been hidden because the user has no formal training, and the range of recommendations is similarly limited.  It is expected that you will adapt this survey to match your experience and needs.

Any suggestions?

OTISS is constantly developing to suit our users’ requirements. Please contact us if you have suggestions for how to improve these risk assessments.