Many Australian state government transport authorities are currently developing new types of strategic transport modelling tools, called Activity Based Models, which differ from the strategic models that currently underpin infrastructure and policy planning across the country.

So, what are they and how could be beneficial to Australia’s transport planning future?

What are Activity Based Models (ABMs)?

Activity Based Models (ABMs) represent a significant shift from traditional trip-based models. While traditional models focus on individual trips between origins and destinations, ABMs simulate the daily activities and travel behaviours of individuals. This approach provides a more detailed and realistic representation of travel patterns, capturing more nuanced human behaviours and the interdependencies and connections between different activities and trips.

Activity Based Models (ABMs) simulate the daily activities and travel behaviours of individuals.

 

Differences and potential advantages of Activity Based Models

Activity Based Models are different from traditional four-step models in a number of ways, and these differences have the capacity to deliver deep insights that can effectively guide transport planning. Firstly, ABMs operate at a higher level of detail, which they achieve by representing the demographics of agents (or individuals) and then modelling the activities of individuals and households throughout the day. This makes it possible to glean a more nuanced understanding of travel behaviour – including the timing, purpose, and mode of each trip as well as linkages between different trips throughout the day. Model outputs can also be broken down to look at policy and infrastructure impacts on different income groups, genders or types of households providing an enhanced capability to support equity analysis.

In addition to its heightened granularity, ABMs can be used to predict how people will respond to changes in the transport system (such as new infrastructure, policy interventions, or economic shifts) by simulating the decision-making processes of individuals. The way they do this is by predicting the activities a person will engage in throughout the day (based on factors like socio-demographic characteristics, household interactions and more), before scheduling their timing and then assigning a mode of transport to the journey.

ABM outputs can be broken down to look at policy and infrastructure impacts on different income groups, genders or household types.

 

Through this process, ABMs have the potential to provide a detailed and accurate representation of how people make travel decisions. For example, a morning daycare drop-off by car would be modelled to have a knock-on impact to travel decisions made throughout the day. Overall – these tools can be used to test a wider range of policy impacts in a more intuitive way.

Challenges of using Activity Based Models

ABMs present Australia’s transport planning professionals with a range of potential benefits. However, there is no free lunch in modelling, so what is the cost of this extra functionality? Primarily, Activity Based Models can take longer to develop and then run, and they also can have heavier computational requirements that can raise the cost of each model run (although there are ways to shrink these costs in some capacity). The added complexity can also make it harder to obtain stable enough results for traditional economic analysis.

In Australia, there is also a knowledge and skills gap to consider. Since these models are relatively unknown in a practical sense, the number of people with hands-on experience is more limited. This means producing, implementing and calibrating ABMs is a somewhat untrodden path. However, with interest growing and more applications of ABMs in Australia appearing over time, these gaps are closing quickly.

Activity Based Models in Australia

Several Australian states are at the forefront of adopting ABMs, which might be viewed as a sign of their potential to enhance transport planning and policymaking. At the time of writing, multiple Australian states – including Victoria, Western Australia, New South Wales and Queensland – have initiated projects to develop and implement ABMs as part of their strategic transport planning frameworks.

Australian states have already started exploring and implementing ABMs for planning and policymaking.

 

For Australia at large, there are potential benefits in adopting Activity Based Models, as well as specific situations where using an ABM would be advantageous. Some examples of these include answering nuanced questions like:

  • What are the impacts of complex fare policy changes?
  • What are the equity implications of my policy investment?
  • How can I get an accurate representation of walking and cycling impacts?
  • How will charging road users at peak times impact travel demand throughout the day?
  • What is the income distribution of certain transport users?
  • How will the introduction of autonomous vehicles change travel behaviour?

This level of specificity presents Australian transport planners with new capabilities in their analysis and subsequent results.

Broadly speaking, adopting Activity Based Models is a veritable advancement in transport planning for Australia. However, it’s important to remember that there is no one-size-fits-all model – which is another way of saying that ABMs, while promising, are not the panacea. With that in mind, the benefits that ABMs offer – their added detail and realistic representation of travel behaviour, as a prime example – can improve the impact of policy interventions and infrastructure investments in Australia, helping to create more innovative, efficient and sustainable transport networks.