Essay Example on Provides a cost effective way of testing and evaluating different scenarios

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Provides a cost effective way of testing and evaluating different scenarios Allows the user to test scenarios faster than in real life Offers an insight into the characteristics of traffic system operations that are important allowing the user to make a more informed decision Provides outputs animation that the public can understand At the same time simulation has some disadvantages Requires collection of detailed data on field conditions Needs calibration and validation of the model prior to testing scenarios Requires an understanding of how the model works before assessing the outputs The processes of conducting a simulation study are described in the following section The movement of vehicles in a microscopic simulation program is controlled by different logic There might be logics for car following lane changing merging behavior on freeways and urban routes It is necessary to have a basic understanding of the logic being applied in the simulation model before selecting it It is also helpful to know if the user is given control in modifying or changing the logic in the model Ease of use Each simulation model is different in terms of its ease of use Some simulation models provide an easy to use graphic user interface GUI and have a simple process for data input Some models allow the user to use an aerial photograph or map as a background while coding the network which makes geometry coding much easier

And some models are easy to calibrate validate by providing different measures of effectiveness in a readable format Simulation models provide users with animation of the network Some models have the capability to provide 3 dimensional animations with other details like buildings traffic signals etc and also to allow the user to zoom or pan across networks Most of these animations can be made into movie clips and are great tools for presentations providing a vivid presentation of the benefits of TSP to policy boards and public Most simulation models have a provision that allows for customizing output format It helps the user to have the results in a compiled form rather than a vehicle by vehicle or a link by link basis Sometimes the models also support tracking individual vehicles and this might be useful in the case of transit signal priority Travel time delay queue length number of stops fuel consumptions emissions bus tram wait time are some of the most used outputs Field data is required to conduct a simulation study The data usually required to conduct a simulation is as follows Geometric length of lanes lane widths number of lanes lane assignment length and location of crosswalks Signal timing plans cycle lengths number of phases duration of phases etc for different times of the day Speed speed limits and average vehicular speed Transit vehicle travel times dwell times and distribution of dwell times The actual amount of data collected depends on available budget time and project requirements

At a minimum a m and p m peak data should be collected If there is a significant variation in traffic volumes additional data may need to be collected such as midday Saturday and Sunday Attention should be given to the time period of data collection For example data collection of regular weekday traffic should be conducted between Tuesday and Thursday to avoid traffic fluctuations due to weekend trips and preferably should not be during a holiday season Weekend data should be collected during times that are most relevant to meet project objectives such as weekend traffic peak period and or weekend peak transit operational headways Developing the network for simulation involves the processes of coding calibration and validation Calibration and validation are extremely important but often do not get the attention they deserve in the simulation process Coding Coding is the process of building the network in the simulation model It involves input of the study area geometry in the simulation model with other information like the timing plans and volumes Given below are the different ways to code a network in a simulation model The network can be coded in the simulation model itself

 The network can be coded in a Network Editor that is bundled with the simulation model and can then be transferred to the simulation model The Network Editor is designed to simplify network coding In some cases the network can be coded in simulation or optimization models and can be transferred exported to other simulation models This procedure is mainly used when multiple softwares are required for the analysis and optimization of the network Sometimes due to the simplicity of the Network Editor the study network is coded in one model and then transferred to another model If this method of coding the network is used the user should be aware of the features elements that may be altered or missed during the transfer process Calibration Simulation models need to be calibrated before they are used for testing future scenarios since an un calibrated model might lead to skewed results Calibration involves changing some of the default parameters used in the simulation model so that it reflects the conditions observed in the study area As previously mentioned the movement of traffic in a simulation model is governed by different logics Simulation models provide the user with different parameters to fine tune the logic and other aspects of the model Examples of these parameters include minimum headway minimum acceleration rate minimum deceleration rate maximum acceleration rate etc These parameters are give


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