Treatments
Introduction
On this page, we provide details of the Treatment Types that are considered in the Default Juno Cassandra Road Deterioration model. Different sections discuss the following aspects:
- Which types of treatments are considered, and for which conditions
- How candidate treatments are selected to be considered in the optimisation stage
- What the impact of the various treatments are on the predicted condition.
Treatment Categories
Before we provide details on the different treatment types in the model. It is important to understand the different categories of treatment because it is the Category that determines what the underlying maintenance strategy is for each element.
The following Treatment Categories are handled in the Default Juno Cassandra Road Deterioration model:
- Preservation/Resurfacing Renewal
- Rehabilitation
- Holding Action
Preservation/Resurfacing Renewal Treatments
Preservation or Surface Renewal Treatments are those treatments that are applied mainly as a preventative maintenance measure. These are treatments that are placed to ensure that the pavement surface remains safe, durable and waterproof. Preservation treatments are thus NOT placed to fix distresses but to prevent distresses from developing and extend the life of the pavement structure.
Preservation plays a critical role in proper Asset Management and the extent of preservation treatments included in the Forward Works Plan (FWP) can be seen as a measure of the health and maturity of the resource planning component of the Asset Management task or system.
Under some funding schemes, ‘Preservation’ may be defined as Routine Maintenance activities such as cleaning of drains, crack sealing while Resurfacing is regarded as ‘Renewal’. Note that, in this Cassandra Default Road Network model, Resurfacing is placed under the ‘Preservation’ category while routine maintenance activities are placed in a separate category deemed to be included in the specified Routine Maintenance treatment.
Rehabilitation
This treatment category aims to significantly restore the pavement structure to its original functional condition. This includes restoration or replenishment of the pavement structural capacity.
As described below, the Cassandra Default Road Network model allows for several classes of rehabilitation to acknowledge the differences in treatment cost and intensity for High, Medium and Low traffic classes. The model also distinguishes between rehabilitation for Asphalt-and-Chipseal-surfaced roads.
Holding Action
Holding actions serve as an intermediate step between Preservation and Rehabilitation. This treatment category addresses the following situations:
- Pavement distress is not sufficient to warrant a rehabilitation but too extensive to perform a Preservation/Resurfacing treatment.
AND/OR
- There is not sufficient funding to perform a rehabilitation, and therefore a Holding Action is placed to mitigate deterioration and keep the pavement at an acceptable level of service.
Achieving an optimal balance between Preservation, Rehabilitation and Holding Action treatments is one of the primary tasks of Infrastructure Deterioration Models. In Cassandra, there are two optimisation approaches to help with achieving an optimal balance between the different treatment categories. You can read more about these two approaches at this Cassandra documentation page in the Juno Cassandra documentation.
Treatment Types
The treatment types defined for the Default Juno Cassandra Road Deterioration model is shown in the table below. Note that this table is formatted to serve as the treatment definition table for defining domain model treatments in Juno Cassandra. More about this can be found on this page of the Cassandra documentation.
Note that, the Unit Rates shown in the above table are the default rates for the Default Juno Cassandra Road Deterioration Model. At the project level, you can override these unit rates without having to modify the default domain model. More about this topic can be found in the Cassandra documentation page dealing with the storage of model setup data.
Also note that the unit rates for some treatments, such as Preseal Repairs and Routine Maintenance, is a dummy unit only, since the actual cost is calculated at runtime based on the quantity of distress that is present, and this is then multiplied with a scaled unit rate which is specified in a Lookup table.
The above table shows that in addition to the treatment category (defined in the first section above), there is also a Budget Category. As with unit rates, you can override the Budget Categories applied to the default model for your project. For example, the table above has a ‘Preseals’ budget category that is applied to Preseal Repairs on AC and Chipseal roads (top two rows). However, if your agency funds these repairs from another budget (e.g. Rehabilitation or Resurfacings), then you can specify this modification in your Project Level setup data.
Treatment Selection
The selection of treatments is a two-stage process:
Candidate Selection Logic
In this first stage of treatment selection, we select any viable candidates elements to be potentially treated in the current year. This selection is made based on age, condition and other parameters.
Note that, in this stage, there is no consideration of the treatment to be applied. We simply consider which network elements are to be considered as candidates for treatment.
An interactive flowchart that explains the current Candidate Selection Logic can be found at this link. Note that this flowchart is quite complex and some parts of the process are initially collapsed to simplify the display. Follow the legend to see which parts of the flowchart can be clicked to expand the logic.
Candidate Treatment Selection
Once the candidate elements to be considered for treatment are selected, the model will execute further logic to determine which treatments can realistically be considered for treatment. Note that more than one treatment type is typically considered for each candidate element. It is then the job of the optimisation algorithm to determine the optimal set of treatments to be applied to which candidate elements.
The selection of viable treatments is a filter process that removes treatments from consideration where they are clearly not suited based on the current condition. For example, if an element has a surfacing with zero or negative remaining life and minimal distress, it may be selected as a candidate for Preservation Treatment. Given that the element has minimal distress, Rehabilitation will typically not be considered for that element during optimisation.
Similarly, for an element selected because it shows significant structural distress, only Rehabilitation or a Holding Action will be considered during optimisation, with all Preservation treatments considered to be non-viable.
Refinement of Treatment Selection Thresholds
As the Cassandra model loops over all modelling years, the candidate element and treatment selection logic removes unrealistic elements and treatments from consideration for the current year. This process lessens the computational burden during optimisation and leads to better short-and-long-term Forward Works Programmes.
Naturally, each network/project has its own unique set of characteristics, and the thresholds applied to select elements and treatments may differ from one network to the next. The Default Juno Cassandra Road Deterioration model makes it easy for you to modify thresholds associated with treatment selection. You can do this by creating a sub-set of Lookup Tables that you can then customise for your network.
The table below shows some of the thresholds used in Candidate Selectin that can be modified specifically for your network or project:
