Is there any point to modelling anymore?

Modelling World International talking point

Ali Inayathusein, National Director, Future Transport at Veitch Lister Consulting, will be speaking at Modelling World International about the successful use of models to predict the new normal. Do you think that our existing models are up to the task, asks Tom van Vuren, Chairman of Modelling World International.

Ali Inayathusein: In our case we used MABM which is largely Agent and Activity based. I think all models can offer plenty of valuable insight, but only if we make appropriate input assumptions to reflect paradigm shifts associated with for example working from home and the perceived attractiveness of public transport. The gap is in obtaining a robust behavioural understanding of these shifts by collecting survey data to inform models rather than alter the frameworks themselves. Having said this, a move towards ABMs will allow us to better reflect some of these phenomena more robustly, and I think LUTI models that explicitly reflect the impacts of working from home on location decisions by workers and employers will also see greater emphasis.

Tom van Vuren: Can you give examples of how you have updated the models to reflect a possible new normal? 

Ali Inayathusein: We used a range of survey and travel volume data sources to understand mobility trends in cities that were ahead of Melbourne at the time of lockdown, to inform short term “COVID-19 normal” scenarios. We adjusted trip-making for agents assumed to work from home in a way that reflected not only changes to work trips, but also other trips in their daily itinerary in a consistent manner and we adjusted public transport alternative specific constants to influence mode shares.

Tom van Vuren: Inevitably, uncertainty about the future has increased. Some might say that the future is so uncertain that there is no point in modelling anymore. What is your answer? 

Ali Inayathusein: I would say that it depends on what you expect models to do. If you only want them to tell you what the future will be then, yes, there is too much uncertainty. However, models should also be tools to explore how policy and infrastructure interventions may be impacted by a range of possible futures. Without models, we just can’t explore and explain the interactions between many complex behavioural mechanisms leading to sometimes unexpected outcomes.

Tom van Vuren: I have often said that we should talk less about the models and more about the assumptions that go in. Can you give me some examples of the assumptions you had to make and how you sourced them? 

Ali Inayathusein: You’re right, assumptions are key. In Melbourne we had to make assumptions around the level of working from home that would persist, at least in the short term. We looked at Google home and workplace activity from other Australian cities, and particularly Auckland, NZ, to get an idea of how trends might progress. We then applied adjustments to workers (model agents) by industry based on a recent intentions survey. In order to adjust public transport attractiveness, we looked at the decline in public transport volumes seen in other cities in a COVID-19 normal scenario. It is important to be explicit and transparent in making these assumptions.

Modelling World International will run from 20 to 21 April, taking place across several time zones. It will feature live plenary debates that discuss local, regional and global challenges, expert modules and breakout sessions covering the latest best practice, innovation and thought leadership. Even better, if will give professionals across the world a unique opportunity to network with international colleagues and connect transport and pedestrian modelling professionals, advisory and strategic modellers, data scientists and transport economist in international debate, enabling discussion of the biggest questions of the day – all virtually. All sessions will be available to delegates on-demand following the live sessions

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