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Transit Assignment Transcad

Programming TransCAD and Batch Mode Processing

TransCAD provides a wealth of facilities for building integrated model applications, performing scenario management, creating custom user interfaces for planning models, and running demand models without user intervention (i.e., in batch mode). In addition to running models interactively, TransCAD provides great flexibility in building complete model applications, with attractive user interfaces that are easy to learn and use. Models can be compiled and published or distributed to third parties with their key properties locked down to protect inappropriate modifications.

TransCAD comes with its own scripting language, GISDKTM, the GIS Developer’s Kit. GISDK is a simple object-oriented scripting language that provides hundreds of powerful modeling and GIS functions. GISDK includes a compiler and a debugger and provides all the tools needed to create model scripts, build add-ins to automate repeated actions, or create custom applications. TransCAD can also be scripted with Python and called from any .NET language.

Innovative Interactive Batch Capture
There is an innovative batch processing system that is built in to TransCAD. In addition to creating scripts the old fashioned way by writing them from scratch, TransCAD lets you create scripts interactively by clicking menu items, choosing parameters in dialog boxes, and saving the corresponding script. This can then be edited further in the conventional manner.

Caliper also provides templates for common modeling streams including feedback so that you can adapt the templates for your own purposes. The GISDK and the batch facility let you create beautiful Windows user interfaces for your models.

User Friendly, Push Button Model Interfaces and Scenario Manager
For most planning models, Caliper offers a pre-designed model user toolbox interface that can be easily modified for your model. The Model User Interface Toolbox provides a custom interface that allows you to run a model with the click of a button, as well as provides features to store and create scenarios. You can generate and store any number of scenarios. Scenarios are defined by a scenario name, a set of input files, output files, and model parameters, and there are special features in the toolbox to assist in setting up scenarios. Once you have setup a scenario, the model steps for a scenario can be run separately or run as a group. With a click of a button you can graphically view model outputs and scenario differences.

TransCAD Model Manager
The TransCAD Model Manager is a graphical environment for building integrated travel demand planning models and running scenarios. The Model Manager allows you to create, understand, and edit planning models based on a flowchart interface. It also provides a wide variety of advanced scenario management tools.

With the model manager, you can interactively specify the order of the modeling steps to be performed, select all of the input and output files, and edit the model procedure parameters. The easy-to-use interface also documents the model and its components, and makes it simple to set up distributed processing.

Scenario Management
The model manager includes a powerful scenario management facility.

Once you have a working model, you use the Scenario Toolbox to organize the parameters for different runs of the model and to run the scenario. The Scenario Toolbox is the control panel for creating new scenarios, for editing and reviewing their parameters (input and output data files), and for running the model under different scenarios.

Object-oriented methods are used to maintain the relationships among sets of interrelated scenarios. Each scenario allows use to define the base directory that the model files use and optionally all the relevant input and output file names and parameters for the scenario. Additionally, sub or "child" scenarios can be created that is a subset of another scenario. The child scenario by default inherits all parameter values from its parent. Whenever the parent scenario’s parameters change, the child's values change automatically greatly streamlining the model process.

Vehicle Routing and Logistics

TransCAD includes a comprehensive library of logistics procedures that apply to all modes of transportation and can be used to solve a variety of logistics problems.

Vehicle Routing/Dispatching
TransCAD provides a rich set of tools that solve various types of pickup and delivery routing problems. These tools are used to prepare input data, solve the routing problem, and provide tabular and graphical output of the resulting routes and vehicle schedules. The TransCAD procedures can solve many variations on the classic vehicle routing problem, including restrictions on the time when stops can be made, the dispatching of vehicles from multiple depots, and the use of non-homogeneous vehicle fleets. The vehicle routing procedure in TransCAD is also capable of solving problems involving mixed pickup and delivery. Once a solution is found and the results displayed graphically, users can edit the routes interactively by adding or removing stops. Once stops have been added or removed, users can perform a re-optimization of the route so as to minimize time window violations.

Arc Routing
Arc routing problems are a class of problems that involve finding efficient ways to travel over a set of links in a transportation network. Arc routing has a large number of public and private sector applications, including street sweeping, solid waste collection, snow plowing, mail delivery, and other door-to-door operations. In a typical arc routing problem, people or vehicles are dispatched from one or more depots to traverse a set of service links. The result of an arc routing problem is a set of one or more routes that cover all the service links with the minimal amount of deadheading.

Network Flow and Distribution Analysis
TransCAD includes a set of procedures for solving network flow problems. These problems involve efficient delivery of goods or services, and arise in transportation and many other contexts.

  • The transportation problem involves identifying the most efficient way to service a set of destinations from a set of origins. For example, a company may be interested in finding the least-cost solution for shipping commodities from its warehouses to its vendor locations.
  • The minimum cost flow problem is a more general version of the transportation problem that takes link capacities into account. For example, the procedure can be used to find multiple paths when capacity constraints make it impossible to utilize the shortest path for an entire shipment.
  • Matching problems try to find the best one-to-one matching between two groups of objects where there is some quantitative measure to be minimized or maximized. For example, you can efficiently assign work to service centers.

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