Treatment Optimisation

Overview

Juno Cassandra currently supports two approaches to support the selection of optimal treatments subject to a budget constraint. These two methods are:

• Benefit-Cost Analysis (BCA) model; or
• Multi-Criteria Decision Analysis (MCDA) model.

The differences between these two models are detailed in the Juno Cassandra documentation.

A brief summary of these two model types in the context of the NZ Local Authority models is provided below.

Benefit-Cost Analysis Model

The BCA model relies on an objective function to estimate the long-term costs and benefits of different treatment strategies. An Incremental Benefit-Cost Analysis is then run to select optimal treatments under a given budget constraint. The BCA method is highly influenced by the cost of treatments and may tend to select shorter and less expensive treatments under a tightly constrained budget.

With the BCA model, you can also incorporate exogenous factors such as climate resilience, route priority etc. into your treatment selection process. However, this may be more difficult than with the MCDA-type model because you need to incorporate these factors into your Objective Function very carefully to ensure the model still gives the desired outcomes.

To explore more details on how the Objective Function is calculated in the Default Juno Cassandra Road Deterioration model, please refer to the Model Definition File.

Multi-Criteria Decision Analysis Model

The MCDA model scores candidate treatments and elements based on a selected set of attributes, each of which can be weighted. These attributes can be divided into two categories:

• Attributes pertaining to the element Site (e.g. traffic, route priority)
• Attributes pertaining to the treatment candidate (Suitability and Cost)

The Treatment Suitability is expressed by means of a Treatment Suitability Score (TSS) which is calculated on the basis of the element condition, age etc. in the current period. Thus, when an element is in good condition but with a relatively high surface age, the TSS for a preservation treatment will be high while the TSS for a Rehabilitation will be low or negative (meaning the treatment option is not considered).

The MCDA model makes it easier to incorporate exogenous factors such as climate resilience, route priority etc. into your treatment selection process. These elements can also be incorporated in a BCA analysis, but it requires more care and exploratory analysis to ensure your Objective Function correctly incorporates and weighs such factors.

To explore more details on how the Treatment Suitability Scores and Multi-Criteria Weighting are determined in the Default Juno Cassandra Road Deterioration model, please refer to the Model Definition File.