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Transport Modelling. Microsimulation Software. Traffic Models. The analytical models are, where the solution to a set of differential equations describing the traffic system is obtained analytically (using calculus) Analytical models can be static and dynamic
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Transport Modelling Microsimulation Software
The analytical models are, where the solution to a set of differential equations describing the traffic system is obtained analytically (using calculus) • Analytical models can be static and dynamic • Numerical methods are used for solutions • The simulation models are, where the successive changes of the traffic system over time (space-time dynamics) are reproduced (approximated) in the model. • Simulation models are dynamic • Macroscopic, mesoscopic and microscopic
Traffic Simulation • Simulation: dynamic representation of real world by a computer model • Traffic Simulation: application of computer models/simulations for • scientific research in planning, training and demonstration purposes • MAIN FACTORS INFLUENCING RESEARCH IN SIMULATION • Advance research in traffic theory • Advancement in computer hardware technology • Advancement in computer software technology • Development in information infrastructure • Increased importance of traffic and transportation in the society
Aspects of road traffic simulation (1) • Transport networks cover wide physical areas • Large number of active participants or users and interaction among them • Objectives of the participants can be individual or social (system optimum vs. user optimum) • Presence of independent variables outside the control of the operator and the participants (the weather conditions, the number of users, etc.) • The variables can be stochastic (inherent randomness) and time varying in nature • Man-machine system, laws of interaction dependent on human perception
Limitations of traffic simulations • Simulations are resource limited • Resolution: Level of detail • Fidelity: Degree of realism • System size: The network size to be covered • Simulation speed: Speed of simulation compared to real time • Resources: Computational resources, programming time
Analysis of Existing Models • Dynamic behaviour of individual agents is explicitly simulated over both time and Space to generate aggregate system behaviour • ‘Micro’ refers to the resolution at individual Vehicle level – inevitable requirement of detailed analysis • 58 identified models of micro-simulation • Models are mostly developed in North America, Europe, Australia and Japan • Types of organisation involved: Research institutes, universities and industrial organisation
Popular microsimulation models Existing Micro simulation Models
Existing Micro simulation Models • Micro-simulation models are essentially research products • 9 of the popular models are commercial products (AIMSUN2, FLEXSYT II, FRESIM, HUTSIM, INTEGRATION, PARAMICS, THOREAU, TRAF-NETSIM and VISSIM) and are continuously in development
Objectives Existing Micro simulation Models • From model designer point, • Quantify the benefits of Intelligent Transportation Systems (ITS), primarily Advanced Traveller Information Systems (ATIS) and Advanced Traffic Management Systems (ATMS) • Evaluation prior and in parallel with on street operation • study of dynamic traffic control • incident management schemes • real-time route guidance strategies • adaptive intersection signal controls • ramp and mainline metering • toll plazas and lane control systems (lane use signs, electronic toll collection, high occupancy vehicle lane, etc.) • assessing the impact and sensitivity of alternative design parameters
Classification based on traffic conditions Existing Micro simulation Models
Scale of applications Existing Micro simulation Models • The scale of application varies then from small type, about 20 km, 50 nodes and 1000 vehicles, to large type, 200 nodes and many thousands vehicles • PARAMICS can even simulate 1 million vehicles with 3000 nodes • Highly specific objectives (models of the type "other" traffic condition) have a very small scale of application
Objects modelled Existing Micro simulation Models
Modelling Techniques Existing Micro simulation Models • Weather conditions are modelled by the speed-acceleration behaviour (changes in the driver behaviour parameters) or by the free flow speed of vehicles. • Parked vehicles are modelled by a particular destination node, side parking on links, temporary incidents or by a particular state of vehicle. • Commercial vehicles are modelled by parameters such as power, mass, length, privilege on certain lanes. • Pedestrians are taken into account when turning flows interact with pedestrian areas or in extending intersection all red periods to simulate walk periods.
Modelling Techniques Existing Micro simulation Models • Incidents are modelled by lane closure signs, blocked lanes, "scheduled vehicles" and slow vehicles. • Public transport, essentially buses, are modelled by vehicles with fixed routes. • Traffic calming measures are modelled by local speed limits, yield sign objects, Variable Message Signs and route guidance. • Queue spill back is modelled by space constraint in car-following and in link changing. • Weaving is modelled by forced lane changing, special lane changing behaviour, decision rules or lane changing logic. • Roundabouts are modelled by lane segments and yield sign objects.
