Overview of the DSP
The Decision Support Process enables a unified approach to transport infrastructure decision-making. Its defining feature is that decarbonisation, climate resilience and adaptation are treated as part of the same decision, rather than as separate assessments bolted on afterwards.
What it changes for the user
The DSP helps users understand the broader implications of infrastructure choices. Three implications in particular run through everything the process does:
| Implication | The question it forces into the open |
|---|---|
| Carbon impact | What does this choice emit, across the whole life of the asset? |
| Sustainability | What does it do to the wider environmental and social picture? |
| Resilience | How well does the network hold up when something goes wrong? |
These are not add-on checks. They sit alongside cost and performance in the same evaluation, which is what allows trade-offs between them to be seen and argued about openly.
Three worked examples
The handbook illustrates the DSP through three different roles, each asking a different kind of question.
An asset manager
Question: what is the environmental impact of this maintenance decision?
A maintenance intervention is usually judged on cost and on asset condition. The DSP brings its carbon and wider environmental consequences into the same comparison.
A senior manager
Question: how does this budget allocation affect network resilience?
Budget is allocated across competing demands. The DSP connects the allocation to a resilience outcome, so the consequence of funding one thing over another becomes visible rather than assumed.
A strategist
Question: which investments address our adaptation or capacity needs, within financial and environmental constraints?
This is the hardest of the three, because the constraints pull against each other. The DSP is built to handle exactly that case: multiple objectives, limited money, and an environmental ceiling that also has to be respected.
Read together, these show the range the process is meant to cover. The same structure serves a single maintenance decision and a multi-year investment strategy.
The modular components
The DSP includes modular components, each focused on one dimension of the decision:
| Component focus | What it contributes |
|---|---|
| Asset condition | The current state of assets, and how that state is changing |
| Risk profiling | Where failure and disruption risk sits, and how much of it is tolerable |
| Whole-life sustainability | Environmental and sustainability performance across the full asset life |
| Climate resilience | How the system copes with, and recovers from, disruptive events |
| System interdependencies | How assets, networks and users depend on each other |
| Spatio-temporal scales | The geographic and time horizons a decision has to span |
Being modular matters for two reasons. Each component can be developed and improved without rebuilding the whole process, and each can be used on its own by an organisation that only needs that one piece.
Where the modules are documented
These components are realised as the seven DSP modules described in Technical modules. The definition of what makes something a module is in Definition of a module.
Where this sits in TPRAF
The DSP is embedded within TPRAF alongside the Integrated Modelling Platform. The DSP defines what needs to be decided and structures the decision; the IMP supplies the quantified evidence that decision rests on. See Integration with IMP.