Skip to main content

Research Repository

Advanced Search

Handling uncertainty in transport planning and decision making - Report of a roundtable discussion held in London on 20 July 2018

Lyons, Glenn

Handling uncertainty in transport planning and decision making - Report of a roundtable discussion held in London on 20 July 2018 Thumbnail



In the 1700s, the French philosopher Voltaire reportedly said “Uncertainty is an uncomfortable position. But certainty is an absurd one.” The transport sector is becoming increasingly alive to how uncertain the future is. There is significant (or ‘deep’) uncertainty about the extent to which existing trends, relationships, technologies, economic and social forces, preferences and constraints will carry into the future. Uncomfortable though it may be, there is a need in our transport planning and decision making to avoid absurdity and address this. This report reflects the insights gained from a roundtable workshop in London convened to discuss the matter.

For some, absurdity concerns the continuation of a longstanding norm in transport planning of appraising future prospects through a reliance on being able to judge what the most likely future is or, in forecasting terms, what the central projection can be considered to be (with management of uncertainty through some form of error band either side of this). Such approaches no longer command a professional or public consensus. The notion of ‘most likely’ is either being challenged or a divergence of views exists over which type of future can be deemed most likely.

Orthodox notions of predicting the future are giving way to scenario planning in which multiple alternative scenarios – substantially different pictures of what course of events might unfold - are entertained. One of the challenges here is in judging whether the true extent of uncertainty is being accounted for, distinguishing between probable (likely to happen), plausible (could happen) and possible (might happen) futures. Views are subjective (and further coloured by opinion on preferable (desirable) futures). This can appear uncomfortable compared to the illusion of a well-defined most likely future that frames the decision making task. Yet the act of embracing and accommodating rather than concealing uncertainty holds the prospect of better supporting and informing decision making.

The following proposition emerges for an approach that may be especially well suited to the early strategic planning and optioneering stages of the policymaking process. Set against a wish to fulfil a high level vision, the aim is to consider the implications of different courses of policy action in the face of multiple plausible futures. Does a course of action align with the vision in each plausible future considered or does it align well in some and not in others? The intention is to reconcile risk and yield. The best course of policy action for one assumed future may give high yield in relation to the vision but may also carry a high risk of misalignment or even failure in other plausible futures. Meanwhile, a course of action which has reasonable alignment across multiple futures may offer a lower (but acceptable) yield but with lower risk.

As becomes apparent from the considerations above, the handling of uncertainty is a wicked problem that is inherently insoluble. It is wicked in the sense that it concerns: (i) divergence in views, understanding and values across stakeholders; (ii) knowledge gaps and a lack of ‘evidence’; and (iii) needing to deal with complex relationships between multiple considerations. This should not imply policymaking paralysis if progress can be made as outlined above in terms of embracing and accommodating uncertainty.

In critically examining how uncertainty has been, and continues to be, handled in mainstream transport planning practice and exploring the prospects for changing this, the following key issues emerged through the roundtable discussion:

Transport planning inertia – Well established approaches, procedures and norms can conspire against developing and adopting new approaches that may be better able to handle uncertainty but which are unfamiliar and potentially challenging to communicate. Acknowledging uncertainty can have connotations of poor confidence and conviction in decisions being made – for example in the context of public inquiries.

Learning by doing – The application of new approaches should be strongly encouraged, with a ‘learning by doing’ philosophy where experiences of those new approaches and the lessons learned are shared with others. Continued dialogue of the sort fostered by the roundtable is important. Guidance should be seen as an accompaniment to this evolutionary approach and as something which itself must be flexible and evolving. The growing signs of transport authorities wishing to take account of deep uncertainty in their decision making are to be welcomed.

Closing down uncertainty – To avoid decision making paralysis, the exposure or opening out of uncertainty through scenario planning needs to be followed by an appropriate process of closing down. Closing down refers to how the exposed uncertainty is then accounted for in informing and enabling decision making. Closing down can take the form of concealing, reducing or accommodating uncertainty and distinguishing between them is important. Uncertainty may be concealed by reversion to focusing upon a most likely future. It may be reduced through better monitoring and understanding of change taking place or through greater effort to control the shaping of the future. Accommodation of uncertainty (as outlined above) involves making sense of what to do in decision making terms with the uncertainty that has been exposed.

Analytical fitness for purpose – Especially in the face of finite time and resources, it is important that the analytical approach supporting each stage in the policymaking process is fit for purpose. There is a risk that emphasis is currently being put in the wrong place in terms of analytical effort and rigour. Heavyweight modelling tools may be used to address a small number of scenarios when, particularly at the earlier stages in the policymaking process, simpler (though not to infer less robust) analytical tools can be more effective in exploring the uncertainty space of plausible futures and enabling dialogue and development of views of actors in the process.

Communication is key – The analytical tools will only ever be a part of the wider process of examining and interpreting the uncertainty faced. It is important that the actors involved in that process - from the analysts to the decision makers themselves - are enabled rather than confused by how the tools are used and their results conveyed. There is a balance to be struck between the breadth and depth of examination of the uncertainty space. There is also a need to recognise the place of both ‘narrative’ and ‘numbers’ in order to ensure effective engagement with actors and to communicate the credibility of, and insights from, scenarios analysis.

Guidance and leadership – The current existence of guidance for appraisal, including the handling of uncertainty, may intend to provide latitude for interpretation rather than ‘rules’ to be complied with. However, this is not always how guidance is treated in practice. As approaches to handling uncertainty are evolved, it will be particularly important that accompanying guidance is enabling rather than constraining. This may require that practitioners are guided on how to use the guidance (with a role for case studies). Leadership will also be critical within organisations in providing staff with appropriate direction, mandate and agency to address uncertainty.

Resources and expertise - We may be facing a perfect storm in transport planning: greater uncertainty over the future at a time of depleted resources and capabilities to address business as usual, let alone the handling of uncertainty. One means of starting to address this would be to consider how available resources can be redistributed across the transport planning and decision making process alongside seeking to reconsider the makeup of experts required to handle uncertainty and communicate it to decision makers. Handling uncertainty must become integral to mainstream practice rather than a bolt-on to it, with the latter risking being misaligned and ignored.


Lyons, G. (2018). Handling uncertainty in transport planning and decision making - Report of a roundtable discussion held in London on 20 July 2018

Report Type Project Report
Publication Date Sep 1, 2018
Deposit Date Sep 27, 2018
Publicly Available Date Sep 27, 2018
Peer Reviewed Peer Reviewed
Keywords uncertainty, scenario planning, forecasting, appraisal
Public URL


You might also like

Downloadable Citations