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TransCAD

TransCAD. Networks and Shortest Paths. Networks and Shortest Paths.

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TransCAD

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  1. TransCAD Networks and Shortest Paths

  2. Networks and Shortest Paths • A network is a special TransCAD data structure that stores important characteristics of transportation systems and facilities.TransCAD uses geographic files to make maps of transportation systems, and networks to solve transportation problems. • Shortest paths are routes over a transportation network that have the lowest generalized cost, where the cost can be any combination of factors such as distance, time, or actual dollar cost of travel.

  3. Link Costs and Other Attributes

  4. Create a Network File (BOS_HWY.MAP) Has to be a line layer

  5. Choose the Active Network

  6. Choose the Active Network from the Network Settings Dialog Box

  7. Create a Lines of Sight Network Path will avoid the obstacles

  8. Shortest Path Overview • There are three ways to solve a shortest path problem: • Using the Shortest Path toolbox to find the shortest path from a single origin to a single destination, with any number of intermediate points • Solving a multiple shortest path an saving it to a route system • Creating a shortest path matrix that contains the costs of a shortest path between a set of origins and destinations

  9. Solve a Shortest Path (S_PATH.MAP)

  10. When you generate a shortest path, you might also want to compute the total value of other network attributes along that path.

  11. Solve Multiple Shortest Paths (M_PATH.MAP) Select the points you want to use as origins Destinations, or Intermediate points. You may use or other selecting methods.

  12. Calculating Point-to-Point Distance (DISTANCE.WRK) Active a dataview with those columns (distance.wrk)

  13. Disabling and Enabling Links in a Network • TransCAD allows you to enable or disable selected links in a network file. This can be useful when you want to temporarily modify the links that can be used in finding a path. For example: • A drawbridge has been raised and you want to find the fastest alternate route in an emergency response situation. • A road is closed for construction and you want to analyze traffic flow after the closure to see where congestion will be most severe. • In a planning application, you are considering two or more scenarios. You can include links for all possible scenarios in the network and enable or disable the links from each scenario as desired.

  14. Disable Links in a Network (LINK.MAP)

  15. Enable Links in a Network

  16. To see Which Links are Enabled or Disabled

  17. Update Link Costs or Other Attributes

  18. Updating Network Link Attribute Fields

  19. How One-Way Streets Are Defined • Every line layer contains a special data field( called Direction or DIR) that TransCAD used to keep track of one-way streets.This field contains a zero when a link is two-way. If the link is one-way, this field contains a 1 or a –1, where the sign indicates the allowable direction of flow: • 1 – Travel is one-way in the same direction in which the coordinates of the line feature are stored(topological direction) • -1 – Travel is one-way in the opposite direction from which the coordinates of the line feature are stored( reverse topological direction)

  20. Display Arrowheads (ONE_WAY.MAP)

  21. Marking One-Way Streets Make a selection first

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