ATAC Researchers Utilize Computer Simulation Models to Analyze Complex Traffic Systems
Traffic simulation models aim to represent roadway networks and traffic conditions for a specific time period. There are various levels of traffic simulation models ranging from macroscopic to microscopic models. Macroscopic models depict traffic flow in a generalized form, such as platoons of vehicles on a less detailed network. Microscopic simulation models use a higher level of detail and are capable of tracking individual vehicles (drivers) on a more detailed network. These models have special algorithms that model specific tasks such as car following and lane changing behavior. Advances in computer technology have resulted in an increase in the number and capabilities of microscopic traffic simulation models. Today's traffic simulation models can produce detailed output and provide fascinating graphics and animation that provide effective tools for both transportation engineers and the general public. The use of traffic simulation models as effective analysis tools has significant benefits. Traffic simulation can be used to investigate and estimate the impacts of making modifications to the network, such as road geometry, traffic control and traffic levels. Traffic simulation can assess these impacts without disrupting traffic operations, implementing costly measures, or causing unsafe conditions to motorists before a design is finalized. The use of traffic simulation can therefore support various decision levels such as operational, planning, and design. One of the main components of a traffic simulation model is the network which includes roadway characteristics and the traffic control devices (traffic signals). Detailed geometric data and traffic signal timing plans are coded for the simulation model. The other main component is traffic data, which include traffic volumes, turning percentage and truck percentages. Traffic simulation models have a component that addresses driver behavior parameters (acceleration and deceleration preferences, car-following, gap acceptance, etc). Usually these factors have a range of default values supplied by the model. However, in order to obtain representative results, additional local data may be needed to calibrate the model. The range of output available from traffic simulation models includes standard measures of effectiveness such as travel speeds, delay and queues. In addition, several customized output data may be obtained depending on the traffic simulation model used. Most traffic simulation models also allow the user to specify how the output is collected and whether they will be for the entire network or a specific section. Traffic simulation models will continue to gain acceptance among transportation professionals as they continue to be enhanced. The traffic simulation models are becoming increasingly valuable tools for modeling complex transportation situations. For more information on the traffic simulation tools used at ATAC, please visit www.atacenter.org. |
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Computer simulation models are often used to study complex systems that cannot be efficiently and accurately modeled with standard analytical methods. These systems are generally stochastic (the outcomes may be governed by random process) and dynamic (the outcomes and system status changes in relatively short periods of time). Modeling traffic operations is a good example of complex stochastic and dynamic systems, and is therefore best suited for computer simulation applications.