S-Paramics Principles, Section 1 : Why Microsimulation?

Road traffic microsimulation is a computer modelling system which represents the behaviour of individual vehicles and their drivers in a road network. These are modelled to observe the rules of the road and to interact with other road users through simple rules. The cumulative effect of modelling individual vehicles is to realistically represent road traffic flow on a physical road network. Microsimulation is a powerful communications tool because it is able to present its outputs as a real-time visual display.

Microsimulation, exemplified by S-Paramics, is a very different methodology from deterministic traffic modelling, as used by SATURN, TRIPS and VISUM. These ensure that a particular solution will always result from a particular set of input data. In reality, traffic data is rarely constant and repeatable, and the microsimulation methodology has been developed to enable traffic modellers to produce design solutions which encompass variability.

Deterministic systems are unable to address situations for which they have not been specifically designed, and this presents problems for using them as a predictive tool. The interactions in congested road networks produce complex effects, and microsimulation is able to spontaneously represent these and enables traffic modellers to understand their designs in a context of high traffic volumes.

A microsimulation model can test in detail the effect of redesigned road layout, changes to traffic demand and traffic control and intelligent transport systems (ITS). As in real life, modelling small local schemes and effects can have a significant impact on traffic flow over a wide area, an effect that other modelling methodologies have difficulty in reflecting.

Interfaces from S-Paramics to ITS and Urban Traffic Control systems enable simulation models to be used to develop control strategies for incident and event management and to investigate options for optimising adaptive signals, and urban or motorway control systems.

The strength of S-Paramics is its ability to apply microsimulation to large area models. The micro in microsimulation reflects the level at which the interactions between vehicles is modelled, not a limit to the extent of the geographical area covered. Large models may extend to hundreds of square kilometres, and the ability to apply the inherent fidelity of microsimulation to wide area traffic issues makes S-Paramics an invaluable tool for traffic modellers.