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Works Plan Considerations

Things to think about beforehand​

There are a number of decisions that go into creating a Treatment Set and consequently a Works Plan. These decisions play a major part in determining how your Network assets are analysed and processed to determine a suitable programme of future works.

To maintain a consistent model across all Horizons users, some of these decisions have to be made centrally. Other decisions can be made regionally and at your discretion, according to the needs and responsibilities of your organisation.

Here are some things to think about before embarking on a Works Plan!

Central Decisions​

Asset Groups​

To predict the future condition of different assets, the Network must be categorised into Asset Groups, which are expected to behave and deteriorate similarly over time. This grouping allows behaviour to be estimated over a larger sample size, as opposed to individual Sections. The grouping is designed to take various factors (e.g. construction type, lane, loading) into consideration, while keeping the number of groups small enough to be manageable.

Condition Parameters​

Horizons is a data-driven tool. Condition Parameters form the basis for its approach to modelling. Condition Parameters are derived from imported data, typically in the form of standardised data collected during various survey types. You must decide which Condition Parameters are important for modelling the condition of your Network assets. The state of each Condition Parameter is projected into the future to decide the Treatments required.

Deterioration curves​

For each Condition Parameter, you can define deterioration curves that model how the parameter is likely to degrade over time on different Asset Groups. This can be calculated from historical survey data or using a linear/quadratic equation. Horizons uses this to predict the future condition of your assets and determine the most effective Treatment(s) for each asset Section. Therefore, it is crucial for these to be as accurate as possible.

Treatments​

You must define a library of possible Treatments that can be applied to your Asset Groups. Each Treatment describes possible scheme lengths, costs, and the effects it has on various Condition Parameters. Treatments are grouped into hierarchical Treatment Sets. Horizons uses Condition Parameter values from past surveys, together with deterioration curves, to determine the most suitable Treatment(s) to apply to assets.

Treatment Sets​

A Treatment Set represents one or more hierarchies of Treatments, typically arranged in descending order of severity. For each Condition Parameter monitored by the Treatment Set, you can partition the range of possible values into different severity bands. For each Treatment in the set, you can then define which Condition Parameters it can be triggered by, depending on which severity bands their values fall within.

Treatment Sets serve as the foundation of Works Plans. They perform most of the Analysis modelling and determine which Treatments are initially triggered for assets (before any constraints are applied). Therefore, it's important to understand how Treatment Sets work and configure them according to your needs, before using them in Works Plans. There's no limit to how many you can create, so feel free to experiment!

Subsection Length​

The Analysis process begins by resampling the surveyed condition data into fixed length subsections. The subsection lengths are set to 10m by default to balance the resolution of national surveys against the efficiency of processing the data. You can customise this in a Treatment Set's settings.

Minimum Length​

When resampling each asset Section into a set of fixed length subsections, there can be a remainder at the end of a Section that forms a shorter subsection. You can limit the size of this in a Treatment Set's settings, so that any subsection shorter than the minimum length is merged with adjacent subsections. This can improve the efficiency of performing Treatments.

XSP Merging​

By default, Treatment schemes are calculated separately for each XSP (e.g. road lane, kerb, footway) on your assets that survey data exists for. However, these schemes can be merged across multiple XSPs for efficiency. In a Treatment Set's settings, you can choose whether merging only happens across XSPs that flow in the same direction (e.g. all lanes on the same side of a road), across all XSPs, or no merging happens at all.

Regional Decisions​

Network​

Each Treatment Set and Works Plan processes all asset Sections on the selected Network. When creating a Treatment Set, you can choose which Network will be analysed, based on the availability of local, regional or national data. Networks can also be divided into Subnetworks, for even more control over the scope of Treatment Sets (and therefore Works Plans).

Budget​

When creating a multi-year Works Plan, you can constrain the Treatments for any single year by using a Budget. This lets you define the maximum possible cost of Treatments across a range of financial years. Any years beyond this are calculated automatically, according to the inflation rate you set.

Strategies​

You can define any number of additional Strategies that set maximum limits for condition values, emissions targets, or backlogged maintenance costs. These can be used to impose additional constraints on Treatment selection for each year of a Works Plan.

Use Local Strategies to define minimum service levels, by setting thresholds for specific Condition Parameters on asset subsections.

Use Network Strategies to meet defined key performance indicators, by setting thresholds for statistics calculated across the Network overall.

Priorities​

It's possible for a Works Plan to prioritise Treatment schemes based on their geographic location. You can define a Priority based on one or more Layers that already exist in your Horizons project. Each style in the Layer(s) can be assigned a weighting between 0 and 1. When a Works Plan analyses an asset subsection, each Priority Layer Style that overlaps the subsection will increase the likelihood of its Treatment scheme being selected for the current scenario.