Posted on: March 3, 2021 at 3:24 PM    

Every year, road controlling authorities in New Zealand spend billions of dollars on extending, upgrading, and maintaining the country’s road infrastructure network. Long before shovels meet dirt and even before design concepts are mocked up, transport planners invest time and effort in identifying and prioritising possible future infrastructure improvements. In the absence of a crystal ball, doing this relies on the expertise of staff who have an in-depth knowledge of transport and are equipped with the right tools. In the Strategy & Planning team at Abley, one of the tools we use to evaluate the future performance of transport networks is Paramics Discovery, a traffic microsimulation package developed by SYSTRA Ltd, and one that we consider particularly well-suited to this purpose.

Traffic microsimulation is a powerful tool that allows us to investigate and visualise the impact of changes to local transport networks by modelling traffic at the closest level: that of the individual road users. The key to this approach is that road users are represented in the model with their own physical space, allowing their interactions with other road users and their environment to be considered. Unlike with macroscopic modelling techniques, where road users are aggregated into numerical representations of flow for use in mathematical models, in a microsimulation model they are modelled as an independent, dimensioned entity with a position and a velocity over a series of timesteps. Each of these entities has its own behavioural profile made up of a set of randomly generated characteristics that reflect the range of user types we see in the real world and dictate how they move about the model. The result is that microsimulation is able to take into account the wide range of small, real-world interactions between users that add up to delays and eventually lead to changes in route choice.

SYSTRA’s Paramics Discovery is a modernisation of the much-lauded S-Paramics software which had been prominent in the transport planning world since the 1990s. Compared to its earlier incarnation, the newer Paramics Discovery boasts simplified network coding and an improved graphical output that has slashed the time needed to build microsimulation models. Reporting has been streamlined to deliver informed and attractive outputs which help us communicate the findings to our clients.

Of course, one of the core tenets of traffic modelling is that we should use the appropriate approach and software for the problem being investigated. Using microsimulation to tackle an issue that could have been solved with intersection modelling software is inefficient, while the reverse risks arriving at the wrong conclusion. Getting this right comes down to experience and understanding what each method is capable of doing effectively.

Now, I know what many will be thinking at this point: isn’t a discussion on the merits of microsimulation modelling a bit out of touch with the direction of the transport industry, and indeed the world, is heading? After all, traffic modelling remains primarily focussed on keeping motorised vehicles moving through the road network. This seems diametrically opposed to environment- and wellbeing-conscious planning policies targeting uptake of sustainable travel modes. Only months ago, the New Zealand government declared a climate emergency as a part of efforts to reduce the country’s emissions, and the 2021/22-2030/31 Government Policy Statement on Land Transport features safety, better travel options and climate change amongst its four strategic priorities. As a transport consultancy with the stated purpose of ‘inspiring positive change’, Abley is fully on board with these policies and thus has a responsibility to ensure the work we do is helping towards achieving them.

In our view, using tools like microsimulation models becomes more important than ever in working towards achieving these policies. If we are to reduce the transport network’s impact on the natural environment and make our cities and towns more liveable, then increasingly difficult choices are going to need to be made. We can see it happening now as cities are increasingly implementing interventions aimed at improving travel for sustainable modes in city centres that range from traffic calming and speed limit reductions to shared spaces.

Traffic microsimulation, after all, is only a tool – and as with any tool, the mindset of the user counts for as much as, if not more than, the capabilities of the tool itself. While some microsimulation models may not explicitly model pedestrians and cyclist activity, it can certainly look at their effects on the road network – which can often be a primary contentious issue around implementing sustainability-focussed schemes. Demonstrating that effects on the wider road network can be mitigated is a powerful card to hold, and with microsimulation this can be done in a way that is visually enticing. With the speed and ease with which scenarios can be tested with state-of-the-art models, we can look at the effects of sustainable transport measures, either by directly including them in the model or by proxying their effects. These measures can include:

  • Traffic calming, pedestrian crossings and speed limit reductions;
  • Raised safety platforms, raised intersections, pedestrian protection at signalised intersections;
  • Restricted access streets, shared spaces and road closures;
  • Public transport route modification and bus / tram priority; and,
  • Temporary effects due to events and construction.

Furthermore, microsimulation models are scalable and can therefore apply equally well to a range of environments. At Abley we have used microsimulation modelling to look at everything from discrete intersections and corridors to small regional centres (e.g. Cromwell, Central Otago District Council) to large satellite towns (e.g. Rangiora, Waimakariri District Council) to metropolitan centres (Dunedin City Council).

If you’re looking to make positive changes in your town or city but are concerned how those changes might affect the existing transport network, get in touch with the Strategy & Planning team at Abley. We’ll be able to point you in the right direction – whether it involves microsimulation or not.

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