National transportation systems, often laid down over decades or centuries, are under pressure to change to reflect modern social, sustainability and efficiency paradigms. To achieve this change, they have to be understood in detail first. But the ability to predict, forecast or simulate changes to a national transport system is limited.

We were asked to create a model that identified and predicted the effects of changes on New Zealand’s transport infrastructure.

Shaping transport systems for a coherent future

New Zealand’s Ministry of Transport is responsible for shaping New Zealand’s transport system, but understanding the impacts of any regulation, policy or investment on such a vast, diverse, and interconnected system is challenging. With a new direction focused on a transport system that delivers positive social, cultural, economic, and environmental outcomes, how can the Ministry take a strategic, integrated approach to ensure a socially equitable and sustainable transport system?

Collaborating to create an Agent Based Model

The Ministry is partnering with Arup to develop a countrywide agent based model (ABM) to examine and assess the impacts of transport system changes in a unified, systematic manner. The model seeks to replicate the multiple interactions of individual movements (the agents) to understand how complex systems function and evolve. This will allow a range of policy questions to be explored based on real time current data. It will allow the New Zealand government to look at how new infrastructure or road pricing affects travel behaviour, for example, and to assess the social and environmental impacts of such changes. 

Our teams from New Zealand and London, working with the Ministry, have co-designed the plan for developing the simulation model for New Zealand to help improve its ability to plan and evaluate potential changes to the transport system and ensure a more sustainable future. The new model will support decision making through better use of data, technology and innovation to help navigate the transport challenges coming in the next 5-50 years.

Overcoming national challenges

In 2018, the Ministry developed the Transport Outcomes Framework. This sets out a new direction for New Zealand, increasing the focus on mode-neutrality to improve the long-term sustainability of the transport network. For the project to be successful, it is important for the model to respond to the needs of all individuals.

We created a vision with a set of design principles for building the simulation and engaged with key stakeholders over a three-month period to understand requirements and priority policy questions centred around five connected outcomes – inclusive access, economic prosperity, healthy and safe people, environmental sustainability, and resilience. The process highlighted a number of potential use cases to inform the model’s development and its value.

Modelling travel behaviours

Traditional methods to tackle similar national and local challenges often involves making sense of aggregated data. This provides high-level, sensible estimates for transport service performance, but limits how we can explore, slice, and integrate the data. Agents represent real people in a given area with daily activity plans including the way they interact with the transport network. Typically, ABMs tend to simulate the interactions of individuals on a smaller scale, such as within a city. In New Zealand, however, we needed a much broader approach.

Ultimately it is not a transport model. It is a social model. There is real opportunity outside of transport if we build a framework where people’s behaviours are better understood. 

Dan Jenkins

Ministry of Transport (New Zealand)

Building a model for a nation

We built the baseline model with the Ministry, with a sample equivalent to 10% of the New Zealand population totalling almost 500,000 unique agents. The model replicates the daily activities of residents i.e. New Zealanders with plans to travel for work, leisure, or other purposes in collaboration with a model of the transport network to define how and where the agents travel. The simulation shows how agents interact with the network and each other. As the model learns and evolves, new behaviours emerge and enable a greater analysis of the impact of policy changes on transport.

Adapting to changing circumstances

Moving forward, we will be expanding the model to encompass New Zealand’s wide mix of transport services, including ferries, airplanes and active modes, to provide a holistic representation of travel activities. We will also be simulating the consequences of transport policy scenarios. The Ministry of Transport is an integral part of the development team, and together we will build the capability to use, develop and maintain the model within the Ministry to help ensure the long-term sustainability of New Zealand’s transport system.