Triple Access Planning

Stress-testing measures against explorative scenarios – how does it work in practice?

By Mojca Balant, Luka Mladenovič, Aljaž Plevnik & Tom Rye, UIRS

Nova Gorica has a long tradition of sustainable urban mobility planning (SUM planning). The city developed its first transport strategy in 2011 and a regional cross-border SUMP in 2015. The second generation of local SUMP was developed in 2017. Currently preparation activities take place for a new generation of the document, which should be developed in 2024/25.

As explained in an earlier blog, in 2022 an exercise was run with transport planners from Nova Gorica and from the TAP for Uncertainty project team which developed a number of explorative scenarios that could be used in future SUM planning. In summary, these scenarios were as follows:

  • Scenario 1: We do what we can but… Commitments regarding the CO2 emission reductions remain on a declarative level. Electric and hydrogen cars are replacing diesel cars, small changes take place regarding public transport and cycling in the city, but most activities remain as they are.
  • Scenario 2: Youth takes over. Bottom-up initiatives manage to engage with wider city population. With strong influence as a result of local initiatives, awareness among residents is raised to the level where people start acting differently even without political, legal, or financial pressure.
  • Scenario 3: Politics leads the way. A strong environmentally oriented administration takes over.  Political decisions lead the way to change. Since the targets regarding CO2 emissions are set very high and not enough has been done in the past years to systematically achieve them, strong restrictions are needed.
  • Scenario 4: Partnership for change. The national government, local politicians and residents reach an agreement that change is needed. They join forces in making the change together. Ambitious policies are put in practice which influence the way we plan, build, and live in Nova Gorica to achieve the net-zero targets.

As the forthcoming TAP Handbook explains, a key possible use for explorative scenarios is to “stress-test” measures proposed in a SUMP, to ensure that they are resilient to several possible futures and, if they are not, to consider changes to them, or possibly removing them from the SUMP altogether.   Looking around the project, it seems however that this stage of incorporating TAP and uncertainty into the planning process has not been tested at other sites. Therefore, in December 2023 the UIRS Transformative Transport Planning research group held a short internal workshop to see how in practice the explorative scenarios could be put to this use.

The measures to be stress-tested were the key measures set out in the 2017 Nova Gorica SUMP.  They are listed below.

  1. Comprehensive mobility plans for key trip generators, especially employers.
  2. Pedestrianisation and missing walking links.
  3. More attractive public spaces.
  4. Elimination of dangerous traffic locations for pedestrians by e.g. slowing traffic, improved crossings.
  5. Better bike connections within city.
  6. Better inter-settlement bike connections within the municipality as a whole.
  7. Better bike parking in residential areas and at destinations.
  8. Promotion of cycling and walking through awareness campaigns.
  9. Improved local public transport, including integration of regular and school public transport.
  10. New vehicle fleet in local public transport.
  11. Parking management and pricing, on-street.
  12. Study to assess demand for more off-street parking, and possible construction of off-street parking garage(s).
  13. Park and ride.
  14. Balancing use of street space between different modes, including in 4 smaller settlements.
  15. More EV charging stations.
  16. Speed reduction especially around schools, traffic calming.
  17. Freight transport management plans

No further information other than these titles was available to the team to understand the measures in any more detail.

Two teams of two people each went through all the measures and related them to each of the four scenarios. The teams were instructed to take a single measure and see how it performed in each scenario both (a) in relation to its impact on objectives in that scenario and (b) in terms of its likelihood of being implemented in that scenario; and to consider about how to adapt the measure in light of these thoughts.

It became obvious fairly early in the exercise that it was a problem that the scenarios developed really only looked at two identified uncertainties (political will and willingness to change behaviour for sake of environment) when there are many others that need to be taken into account. In addition, it may be difficult to have a discussion about the impact of political will on a SUMP with the municipal team that is producing that SUMP. This emphasises the need for a careful choice of key variables in the explorative scenarios, and also the need to ensure that the team doing the stress-testing of measures is the same team that developed the scenarios, so that queries about the validity of and variables in the scenarios are minimised at the stress-testing stage.

As the discussion progressed it became difficult to know whether the exercise should focus on the robustness of the measures in terms of the probability of them achieving objectives in the different scenarios, or their robustness in terms of whether measure would be implemented in that scenario; or both. If anything, the discussion tended towards the latter when on reflection it should probably have focused on the former. In most scenarios, the robustness of measures in terms of the likelihood of their implementation was rather low, because these scenarios are of futures where political and public support for sustainable transport measures is lower than today. In particular, measures requiring significant transformation of roadspace away from cars, or measures increasing the cost of private car travel, were seen not to be robust in terms of likelihood of implementation, in any scenario. This then fed through to the likelihood that they would deliver on objectives; but this was because their poor acceptability made them less likely to be implemented, rather than because the nature of the scenario made it unlikely that their impacts would be achieved. 

The attempt to stress-test measures against the scenarios led the team to question the usefulness of this set of scenarios mainly, as explained above, due to the constraints imposed by the main variables. This made it hard to achieve the main objective of the exercise which was, for the team, to bring a broader approach to the selection of SUMP measures in the light of different possible futures.  Such an approach contrasts strongly with that currently used in Slovenia which is very much a quantitative and predictive one based mainly on the assumption of continuing traffic growth. The value of scenario thinking, but the time that it took Nova Gorica to develop its scenarios and the constraints that those scenarios then placed on the stress-testing measures made the team consider an alternative approach. It could be that instead of an exercise in every municipality to generate explorative scenarios, a set of national scenarios could be developed for everyone (including the national level), to use. These scenarios should be explorative and not just based on the growth of transport demand, but should include things like trends in preferences, ageing, energy prices, land use structure and so on. This could reduce the cognitive effort for municipalities of developing their own set of scenarios and increase their usefulness – including at the national level. 

Thus, in conclusion we can say that the Slovenian exercise in stress-testing measures was not 100 % successful in what it set out to do, but that it generated additional useful thinking about how SUM planning based on explorative scenarios could work in practice.

Triple Access Planning

Uncertainty and the EU SUMP Guidelines – more to consider?

It’s getting on for three years since the EU SUMP Guidelines (Rupprecht Consult, 2019, produced for the European Commission) were published and if there’s one thing that’s become more obvious in that time than it was back then, it’s that we live in an uncertain world.  There are changes, such as in personal preferences about where to live and how to travel, or fuel prices, or the use of self-driving vehicles, that we can foresee, but we are uncertain about the speed and scale of change.  Then there are changes that we simply cannot anticipate – arguably, the pandemic was one of these. The use of digital connectivity as a substitute for physical mobility, and the importance or otherwise of access based on short distances (the 15 Minute City, for example), are concepts that are with us, but how much they will reduce longer distance physical mobility in future remains uncertain as well.  So, in short, there’s a pressing need to try to better account for these uncertainties in SUM planning – perhaps especially so in those SUMPs, such as those financed by the EU in Accession States, that involve, at considerable cost, the construction by consultants of a traditional four-stage transport model using quite linear predictions of the future that, after the SUMP has been produced, nobody in the municipality for which it is built is very certain how to use.

In the Urban Europe project Triple Access Planning for Uncertain Futures we are advocating an approach to SUM planning that takes uncertainty more into account – but how?  Principally, we suggest, by the use of explorative scenarios – this means scenarios, or depictions of the future, that begin on the basis of past and present trends but that lead to credible, plausible futures.  Crucially, these are scenarios that do not package transport measures within a SUMP – they instead  try to take into account (changes in) a range of factors that might influence our futures substantially, such as personal preferences for different forms of social contact, or trends in working patterns.  Packages of measures and the SUMP as a whole can then be “stress-tested” against these scenarios to see how well they perform.  Ratcliffe (2002, p.4) is cited in Mietzner and Reger (2005:224) as listing the “main characteristics of scenarios [as]:

  • present alternative images instead of extrapolating trends from the present
  • embrace qualitative perspectives as well as quantitative data
  • allow for sharp discontinuities to be evaluated
  • require decision makers to question their basic assumptions
  • create a learning organisation possessing a common vocabulary and an effective
  • basis for communicating complex – sometimes paradoxical – conditions/ options.”   

So how is uncertainty dealt with in the EU SUMP Guidelines?  To answer this question, the TAP for Uncertain Futures project conducted a structured review of the 2019 Guidelines and the 2021 Topic Guide on Planning for More Resilient and Robust Urban Mobility.  Leaving aside the issue that digital accessibility is really not considered, and nor is the uncertainty of the future interaction between digital, short distance and long distance mobility as means to access what we need, the main issue is that scenario planning, as defined in Sections 4.1 and 4.2 of the Guidelines, is not based on explorative scenarios as described above, but largely on scenarios defined as different packages of SUMP measures.  The 2021 Topic Guide defines scenarios in the same way but slightly confusingly also mentions explorative scenarios.  However, it says little about the detail of explorative scenario development and planning, and advocates their use primarily as a way to address major shocks such as pandemics rather than a routine part of SUM planning for an uncertain world. 

So while the 2021 publication has in comparison to its 2019 “big brother” begun to recognise uncertainty as something that should be planned for, in brief, there is little advice on how to do so.  It is for this reason that the TAP for Uncertain Futures project, through its research and practical work with five municipalities across Europe as they further develop their SUMPs, plans to produce new practical guidance on how to develop scenarios and better plan for uncertainty in SUMPs in future.

Tom Rye is a Professor of Transport Policy at Molde University, Norway, and a senior researcher UIRS the Urban Planning Institute of Slovenia, and (with UIRS) project partner in Triple Access Planning for Uncertain Futures.