Taking ‘Decide & Provide’ up a gear: vision-led local transport planning

Lots of clients are now seeing the opportunities that come with vision-led planning and DfT’s Common Analytical Scenarios. As a reflection on the evolution in approach we’re seeing (and driving) here at Sweco, this piece looks at how, combined with the Department for Transport’s (DfT) new guidance on uncertainty and Common Analytical Scenarios (CAS) at different stages of scheme development, a ‘re-route’ in thinking could help all stakeholders make stronger business cases for investment.

This includes moving away from the ‘predict and provide’ techniques that have tended to favour maintenance of the status quo, often road-based solutions. By shifting to uncertainty analysis and scenario planning there is an opportunity to consider a range of outcomes including how we would like the world to look (‘decide and provide’). This can be used to make the case for a new generation of vision-based transport schemes and through early application can lead to better outcomes for scheme promoters.

Promoting vision-based value – part of our Outline Business Case for the A641

The problem with (false) certainty

The Department for Transport (DfT) recently released new guidance (Uncertainty Toolkit, 2021 and Common Analytical Databook, August 2022) on the use of scenario testing in transport modelling and planning in recognition of “the fact forecasting future demand is extremely challenging, and that while the ‘core’ scenario is intended to represent the ‘best’ basis for decision making, in practice it is often not possible to robustly identify a ‘most likely’ or expected outcome with any certainty.”

This new guidance is intended to be used throughout the business case process to better understand uncertainty which can be captured in reporting and result in better informed investment decisions. The quotation above highlights a historic weakness of appraisal which has seen an overemphasis on a ‘core scenario’, sometimes mistaken for the most likely outcome. The reporting of transport scheme impacts including benefit cost ratios have often heavily relied on the core scenario and sensitivity tests for high and low growth.

Whilst there are sound motivations for pursuing this relatively simple approach – not least avoiding the added time and expense of appraising multiple scenarios – there is a growing recognition that testing a single core scenario does not fully represent the range of possible futures, which in turn, provides a narrow base for decision making. This can also lead to a situation where a scheme promotor may ‘game the system’ in an effort to secure funding.

An example of this may be where a scheme is optimised to draw the maximum level of monetised journey time savings for the core scenario, rather than taking a more holistic view of the objectives and seeking to maximise a range of benefits (economic, social, environmental, monetised and non-monetised) across a full range of potential scenarios. Whether done consciously or unconsciously, the ‘target to hit’ approach to developing scheme proposals leads to a narrow range of scheme proposals. It also begs the question, what happens if the demand assumptions in the core scenario forecast do not materialise in the future?

Dealing with uncertain times: The Common Analytical Scenarios (CAS)

The recognition that uncertainty could be better represented in analysis using scenario testing was being discussed before the pandemic and was included in the DfT’s Modelling and Appraisal Strategy launched in 2019. However, the recovery from Covid-19 ignited debate about what a ‘new normal’ could and even should look like. Whilst opinions continue to differ on this point, the events of the last couple of years highlights the real-world impact of short-term uncertainty and the need to consider a range of possible futures when planning investments with lifespans measured in decades.

Although a global pandemic with extended lockdown periods is at the extreme end of scenario testing, some of the changes witnessed during this period are captured under the common analytical scenarios. For example, the behavioural change scenario includes for increased use of digital infrastructure and demand for active travel.

The Uncertainty Toolkit provides a framework on using the CAS including proportionate levels of testing based on development stage and the overall impact of a project. For ‘low impact projects’ a fully qualitative discussion may be proportionate through all stages, a larger project is more likely to require full modelling of some or all the CAS. Whatever the impact of the scheme I would advocate for an early consideration of CAS as part of option development to move towards a vision-led approach and in doing this asking how the scenarios reflect the world we want to live in.

Potential Limitations of CAS

Modelling of CAS is recommended for medium and high impact schemes at the Outline Business Case stage. However, by this point a preferred option is likely to have emerged for the scheme so this is most effective as a means of stress testing a proposal and its prospective value for money case. Whilst refinement of design can still take place, it is highly likely a significant amount of development work will have already been completed with limited appetite for revisiting options and therefore further scope for change might be somewhat limited.

Application of CAS could be seen as ‘another box to tick’ rather than an opportunity to also develop better schemes, in turn supporting more robust decision making. It focuses on testing the effects of exogenous factors on proposals that DfT states are “often related to demand-side factors”. Exogenous factors are “external forces outside of the decision maker’s control which may influence the system significantly” and demand uncertainties are “due to current and future economic, demographic, technological, and behavioural change, policy led demand and proposed developments.”

Predict & Provide…

Or Decide & Provide?

This is to say, the CAS are representative of changes in the wider world which are unaffected by the scheme being promoted (endogenous, supply-side factor). This is likely a reflection of DfT’s role in the decision-making process and the need to evaluate the relative merits of transport schemes across the country. For this, a consistent approach to aid comparison is important; hence, a common set of analytical scenarios.

The CAS are undoubtedly a step forward for the purpose they need to serve. However, there is a risk that if we only consider scenarios at later stages of a project that we get a more robust evidence base to support investment decisions, but miss an opportunity to promote different types of scheme at the optioneering (Strategic Outline Case) stage. This reinforces the traditional ‘predict and provide’ (P&P) method where we predict demand using past trends (core scenario) and provide (supply) schemes to meet this demand. TRICS guidance describes how “it (P&P) can be perceived as replicating and reinforcing the status quo”.

This combined with an appraisal process which has been heavily weighted towards monetising value of time savings means that it has often been ‘easier’ to make a strong value for money case for certain types of schemes, often road-based.

The early application of CAS…and how this could lead to better outcomes

If scheme promotors are pro-active and consider scenarios at the earliest stage of option development, there is much greater scope to realise a more vision-based approach – a ‘decide and provide’ (D&P) approach rather than forecast-led ‘predict and provide’ (P&P). The D&P approach has been described as “to decide on the preferred future and provide the means to work towards that which can accommodate uncertainty”.

What would you like the future to look like? Collaborative business case development for the A641

If we are to do this, we must not only think about how a scheme will perform under scenarios outside of our control, but also think about endogenous factors. As stated in the Uncertainty Toolkit “the presence of endogenous factors may lend itself to a more visionary approach to uncertainty analysis, whereby scenarios can be used to explore how policies might help achieve desirable end states.”

Transport for the North (TfN) have been early pioneers of scenario testing in transport “to help futureproof decision-making on the investment needed to deliver the vision set out in the Strategic Transport Plan (STP).”

In an overview, Professor Glenn Lyons, explains that TFN’s “approach involves two important elements: being vision-led; and accommodating uncertainty. It can be summarised as follows:

1. Determine a preferred future – a vision with associated outcomes that is desirable and achievable.
2. Develop a series of plausible future scenarios that helps expose the uncertain context ahead within which efforts to achieve the preferred future will play out.
3. Establish and prioritise options for helping move towards the preferred future.
4. Test how those options perform in each of the plausible scenarios – are they effective in all scenarios (resilience) or are they ineffective (or less effective) in some scenarios (risk)?
5. Compose a strategy for vision realisation that accounts for, with the selected options included, the uncertainty that has been explored.”

Whilst TfN are operating at a sub-national level and therefore on a much larger scale than local transport schemes, there is no reason why a similar approach cannot be applied at the early development stage of all schemes. If we want our transport schemes to contribute towards and complement this ‘preferred future’ then we need to ensure we develop schemes that deliver outcomes consistent with the vision. This is an approach we started to adopt on an Outline Business Case for the A641.

This approach is also hinted at in the Uncertainty Toolkit – “qualitative analysis could consider how the different assumptions used within each CAS will impact on scheme objectives and potential solutions. This should inform sifting and also inform which CAS to focus on when doing quantitative analysis in later stages”

In these resource constrained times, the CAS could be seen as an additional burden due to the time and cost involved in modelling additional scenarios. Instead, I would argue that working with scheme promotors we should seek to set out a vision with desired outcomes and consider using qualitative analysis to evaluate how the long list of scheme options helps realise these. By considering at the option sifting stage and supported by techniques such as the DfT value for money framework ‘Switching Values’ guidance at later stages, we can make a stronger strategic and economic case for vision led projects. Furthermore, by considering how we want the ‘supply side’ to shape the future at the early-stage development we can avoid extra or wasteful work at later stages.

Conclusions

Historically, we have developed transport schemes in this country using the predict and provide method. The ‘predict’ side of this method has often been based on a core scenario which can be misinterpreted as the ‘most likely’ future position with a narrow range of outcomes. This in turn limits the range of schemes being developed and can lead to scheme promotors ‘optimising’ their proposals to maximise benefits that fit in this narrow range. Furthermore, very little is known of how these proposals perform under a range of future forecasts. This situation serves to reinforce the status quo.

Building a sense of place (A641) 

The DfT’s CAS have been developed in response to this backdrop and recommend scenario testing to provide a more robust basis for decision making. This satisfies the requirements of DfT, but could be a missed opportunity for local scheme promoters if not employed from the very earliest stages of option development. If we want to move towards a vision-led, decide and provide approach to transport planning, we need to consider how the vision relates to CAS and how some of these scenario outcomes may be more desirable than others.

We can then start to think during option generation and sifting about how measures may perform in these scenarios. Should the CAS or even additional scenarios be evaluated to make a more compelling case for investment? Although a single local transport scheme may only provide a nudge towards a preferred future on a global level. If we view the guidance in the Uncertainty Toolkit as an opportunity, I think it is possible to enhance development of vision-led schemes and make compelling cases for the investment with outcomes to the benefit of local communities.