Traffic Simulation

Why Would You Use a Traffic Simulation?

What is traffic simulation and what are its advantages? How do traffic flow modelling and simulation work? Where has traffic simulation been put to best use? What is a multimodal simulation? Which software is used for traffic simulation? Here we clarify the most important questions around traffic modeling and simulation.

It is one of the main challenges of our time: The growing need for good mobility - and thus for reliable and responsible means of transportation. We are all familiar with the problems that arise in overloaded transport networks: cities in particular struggle with traffic jams, congested roads, and air and noise pollution.

Our mobility and transportation systems are becoming increasingly complex. Making them efficient and sustainable is in turn becoming an ever-greater challenge. What are the best measures to reduce traffic-related emissions? How can traffic be managed safely for all road users? How to choose between a roundabout or adaptive traffic lights to guarantee a good traffic flow? How to coordinate public transport service with smooth traffic operations?  What impact will new technologies like autonomous driving have on the network?

Traffic simulation is an important tool to investigate these questions. It enables planners to use available budgets and resources as efficiently as possible when expanding or reconstructing transportation systems. Simulation models help to understand the effects that different measures have on traffic volume and traffic flow under different circumstances. So, simulating traffic creates a solid basis for good and cost-effective decisions - making traffic and mobility safe, sustainable, equitable and resilient. In short, it helps to create future-oriented mobility.

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What is a traffic simulation?

A traffic simulation is a virtual replica of real traffic scenarios. In this digital environment, planners can model junctions and corridors and basically any infrastructure - from roads to interchanges and transport hubs. A transportation simulation, based for example on the software PTV Vissim, gives a realistic and detailed overview about multimodal traffic flows and the interaction of different vehicles and road users.  Multiple "what if" scenarios can be defined to test and analyze traffic measures and their effects, before implementing them in the real world.

Microscopic simulation, mesoscopic and macroscopic simulation

There are different resolutions of simulation models:

  • Macroscopic simulation considers only aggregated traffic flow volumes, and not individual agents (vehicle, road user).
  • Mesoscopic simulation is based on individual agents, whose behaviour is determined from aggregated traffic flow attributes, like the density or the average speed. Direct reaction of agents to other agents happens only at nodes (intersections).
  • In a microscopic simulation, each individual agent reacts on their current environment, i.e. the distances and speed differences to nearby agents. The movement is modelled continuously in time and space. Decisions about change of speed and direction happen usually in small time steps of <1 second. The overall traffic state results from the individual decisions of the agents.

The combination of mesoscopic simulation and microscopic simulation in certain network sections is known as hybrid simulation.

What are traffic simulation models used for?

As with an architectural model, a transport simulation model helps to gain a better understanding of a complex system. In cities, pedestrians, cyclists,  public transport and motorized vehicles meet in a very narrow space. And multimodal transport systems do not only consist of different kind of road users, modes, and mobility providers. Aspects like people changing mobility behavior or new services entering the market – such as autonomous driving – also come into play. Simulation models enable traffic planners to understand this highly complex and dynamic system and develop efficient strategies to solve current and future traffic problems.