This topic covers all elements of Deterioration Modelling in JunoViewer Web
Using an Area-Under-the-Curve Deterioration Model
|
Fritz Jooste Administrator Posts: 81
4/28/2020
|
Fritz JoosteAdministrator Posts: 81
When you use a Benefit Cost Analysis (BCA) model in JunoViewer, you may want to use a surrogate parameter instead of actual costs for your Cost of Use (CoU) parameter. For example, instead of using Maintenance Cost, you may want to use a weighted condition indicator such as a Condition Index. Such a parameter would then serve as a surrogate for the CoU. In effect, what your model will do is to try and minimize the area under the curve of your surrogate CoU parameter. This help post deals with such a modelling scenario.
The CoU parameter is critically important for all BCA models since it determines the benefit of different treatment strategies, thereby allowing you to compare strategies and select the most cost-effective method. For details on how Benefits are calculated using the Cost of Use parameter, please refer to this help post.
When using a Area-under-the-Curve approach with a surrogate Cost of Use parameter, the key challenge is that your Cost of Use values are not in monetary terms. For example, if you may want to use a Pavement Condition Index (PCI) ranging from 100 (worst condition) to 0 (best condition) to concisely compare the condition under different treatment strategies. Adding the PCI over all modelling years will then give you an approximate Area-under-the-Curve for PCI.
When using such a surrogate cost parameter, the traditional Benefit-Cost analysis methods such as NPV and Benefit Cost Ratio cannot be used. This is because, as indicated above, the scale of your Cost and the scale of your Benefit may be vastly different. This will most likely result in negative NPV values and/or Benefit-Cost ratios that are less than 1.0.
In such cases, the Incremental Benefit Cost Ratio (IBCR) method can still be used, provided that Benefit Cost Ratio values of less than 1.0 are allowed in the calculation of the IBCR. During the strategy generation process, JunoViewer will always assess projects on the basis of the IBCR to ensure that only projects that are Pareto Optimal are considered in the Global Optimization stage. This is regardless of whether your model is an NPV optimized or MaxBCR Optimized model. The latter settings only come into play in the Global Optimization stage, where strategies are picked on the basis of maximizing BCR or NPV, depending on which model was specified.
The figure below shows a scenario where the Benefit is expressed on a scale of 0 to 100, with the cost of the strategy set ranging from zero to $365,000. Using the IBCR method with a minimum allowable BCR of 1.0, JunoViewer can still identify the Pareto Optimal projects which are shown in red in the figure below. For more information on why the concept of Parato Optimility is used, please refer to this help post.
To summarize: if you need to use an Area-Under-the-Curve approach in your model, you simply need to specify the following three parameters in the General Sheet of your DMS:
1. Treatment Assignment Mode: Any of the BCA Optimized models can be specified (NPV or IBCR or MaxBCR Optimized)
2. Omit Do-Nothing Strategy = TRUE
3. Minimum Acceptable Benefit-Cost Ratio = 0.0
Please Note that if you are using an Area-under-the-Curve approach to optimization, you should ideally not include Residual Value calculation in your model. This is because Residual Value is calculated in terms of actual treatment costs, and as such the calculated RV will dominate your optimization objective such that your model will tend to favour treatments in the last years of the model.
edited by admin on 5/20/2020
|
|
|
0
link
|
