Tip 1. Preventing some errors in TransCAD

When you are working with TransCAD, copy all your data to the C: drive (for example to C:\Temp). Working from the U: drive can create lagging in the data flow due to high network traffic which produces errors in TransCAD. DO NOT forget to copy all your data back to the U: drive after you have finished your work.

Tip 2. Opening files in TransCAD

From the Edit/Preferences dialog - File Sharing tab, you can select how to open files in TransCAD (read only and exclusive access). Uncheck the box for read only and check the box next to Exclusive Access. Repeat this for both cases (Local and Network Drives).

Lab 3: Building Travel Demand Model Zones and Networks

PART 1: ZONE BUILDING

INTRODUCTION: Traffic Analysis Zones or TAZs are geographic areas that divide the planning region into similar areas of land use for modeling the origins and destinations of trips. For example, a residential neighborhood typically has its own TAZ or set of TAZs, as does a community’s central business district or industrial area. These zones are then represented in the network by special nodes called centroids.

OBJECTIVES: Using TransCad, learn the process to define and build a Traffic Analysis Zone layer.

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TRANSCAD TOOLS YOU WILL NEED: Last week, you were exposed to some of the basic functionality of TransCAD. There are a few additional things you will need to learn how to do in order to complete this week’s lab.

Tools-Map Editing (you use this to create new GIS layers – NOT the drawing tools on the main toolbar. If you draw using the main toolbar, the items you draw are cosmetic only and are stored on the “map” not the individual files – e.g., they will not be saved if you don’t save the map and they will always be there even if you turn some layers off) Read the manual or see the online help. You CAN select elements and delete them using edit – delete selected (not edit – delete, that only works for cosmetic elements.)

Make sure your layers are all editable (file is saved as standard geographic rather than compact geographic, and make sure when opening a file the “read-only” box is not checked. Always open for exclusive access if you have the option.) If you find that a map layer is not editable, close the layer (drop it from the map) and re-add it making sure you open it with proper permissions. TransCAD cannot edit any files except those in standard geographic format (dbd). If your file is shape or compact data format (cdf), export it to the dbd format before trying to edit.

Save a collection of files in a MAP, so that your line styles, etc. are the same the next time you open your files. – warning: if you open files that are read only and save your settings in a map, each time you open the map, it will reopen your files as read-only and you will not be given the option to uncheck the read-only box.

TAZ STRUCTURE RULES: Typically a TAZ system should follow Census Geography (block, block group and tract) when possible. This makes the use of census data easier and eliminates complex manipulation of the data.

TAZs should contain land uses that are relatively homogenous in character. Combinations of land use types within a TAZ should be avoided. Physical barriers such as railroad lines, rivers and major roadways should not cut through your TAZs. In fact, it is important that no roadways in your model network cross through a TAZ. Remember, we are trying to replicate the volume on the network that represents vehicles traveling from one TAZ to another.

It is also a good idea to look forward to your planned network when creating your TAZs so they can be created such that they will not need to be modified/split when new roadway links are added for the future year model.

DATA: (make sure you use only the data below for this part – check file names)

AmesDOQ.jpg and related fileStory blocks and data.shp and related files

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Story County Streets.dbd and related filesAnalysis Boundary.dbd and related files

PROCESS:

Tasks:

1) Create a TAZ layer within the confines of the boundary file (Analysis Boundary.dbd).

2) Use the aerial photo (AmesDOQ.jpg), Census Geography (story blocks and data.shp), and Story County Streets.dbd to guide TAZ layer development.

3) Use rules for TAZ boundary definition.

STEPS: (read all steps before beginning – some hints are given in later steps)

1) Open AmesDOQ.jpg. Make sure to select .jpg as file type. If it asks you what coordinate system to use, use these settings:

2) Add the boundary layer named Analysis Boundary.dbd. Use Map>Layers>Add Layer function or the Map Layers icon on the toolbar.

3) Change color and line weight of the boundary to show up better.4) Add the layer (story blocks and data.shp.) Remember to select ESRI

shapefile for file type. When you open it, check the “import” box – that will allow you to save the file as an editable dbd file (if the import box is grayed out, go ahead and open the file, then export the .shp file as .dbd). Drop the shp file and then add the new dbd version.

5) Add the layer Story County Streets.dbd – make sure it is not opened for read only access but that the box is checked for exclusive access.

6) Create a TAZ layer: a) Option 1: you may wish to start a new file

1. FILE-NEW-GEOGRAPHIC FILE-AREA GEOGRAPHIC FILE2. add an integer field called TAZNUM 3. save the file with name TAZ in your working folder and add the file to

your current map

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4. use the map editing toolbar to add TAZ polygons (see next step).b) Option 2: make a copy of the Blocks file and call it TAZ.

1. Use tools-export and save the file with the name TAZ. 2. Add TAZ to your map using the Map-Layers command3. Eliminate boundaries between some blocks to aggregate them to TAZs

using the Map Editing Toolbox (see next step). 7) With the TAZ file as the active layer (notice that layers can be renamed in

layer control and that the layer name is not necessarily the same name as the computer file) use the Map Editing Toolbox to start creating (option 1) or aggregating (option 2) TAZs. How many TAZs do you need? A fair rule of thumb might be around one TAZ per thousand population. This is not to say that each TAZ needs to have 1000 persons within it. In fact, some TAZs may have very little population (e.g., commercial or industrial zones). However, each TAZ should be defined so as to generate more or less a similar number of trips. This is difficult to ascertain before you “generate” the trips, but use your judgment here.

8) Create only 10 TAZs. Stay within the Analysis Boundary. Create “normal sized zones” – assume you would use about 75 to fill the entire area, but create only 10 (you will not cover the entire area). Use the Census block layer and street file to guide you in selecting your TAZ boundaries. We’ll have a real TAZ layer to use for future steps and labs. Don’t worry if minor streets cross into your TAZs, but do not let major streets cross through.

9) If you used option 2, open the TAZ dataview. Go to the Dataview pull-down menu and select “modify table”. Click “Add Field” and name the new field TAZNUM. Also, if you used option 2, plainly tell me which TAZs you created using aggregation. You will have many more TAZs than you need, as all block not aggregated will also be given a TAZNUM.

10) In the dataview, select the column TAZNUM and use edit-fill sequence to add TAZ numbers. This will allow you to label TAZs on your plots. When you close the dataview, you do not need to save it (but you do need to save your map once you are done).

11) Save as a Map file and be sure to back up all your data. It is good practice to check the dates on files to make sure you save all the files that may have changed in each session. Also, file management is critical. Make sure all your files and folders are appropriately named so that you can find things later AND that you do not have duplicate folders. Keeping your disk neat and tidy will save you much grief and make you much more effective.

Deliverables:

1) Create a good looking thematic map showing your TAZs and underlying streets and census block with appropriate labels for TAZs and selected street names (highlighting the ones you created if you used option 2). Use a thematic map to display some relevant data on the block level.

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PART 2: NETWORK BUILDING

INTRODUCTION: The development of Traffic Analysis Zones (TAZs) and the transportation network are interdependent. One of the first steps in the data collection process is the selection of roadways to be analyzed in the model. Typically, roads of minimum federal functional classification are chosen to make up the network (such as minor collectors and above). These roadways define many of the boundaries that make up TAZs.

An important distinction is made between the terms “network” and “line layer”. The entire road system and that seen on the screen is the “line layer”. Once a “line layer” has been developed, it is used to create a “network” or “*.net” file.

The network has six basic components. These are the links, nodes, centroids, centroid connectors, external stations and external station connectors. The link is what represents the roadway. Links are also where the roadway attribute data are stored, such as speed, capacity, functional class, travel time, etc. Breaks in the links are represented by nodes and are often at locations where roadways intersect. The centroid is the network representation for the Traffic Analysis Zone. The centroid is where all trips are generated from and attracted to. Placement of the centroid is designed to replicate the center of activity within a TAZ.

Not all roadways are to be included in the network. Local or neighborhood roads are typically not included in the model. These roadways are represented in general by links called centroid connectors. The centroid connectors represent local streets where trips originating or terminating in the zone access the network. Placement of centroid connectors is dependent upon the size and shape of the TAZs and how traffic should be loaded to the network. Centroid connectors should represent realistic connections from within a TAZ to the arterial street system and not cross physical barriers.

External stations and external station connectors act in much the same way as centroids and centroid connectors. The difference between them is the external stations are located at the periphery of the network or study area and handle all the external trips. These trips could be external-external or external-internal in nature.

Obviously, the network is a critical component in a travel demand model. This part of the lab addresses the development of a network using a variety of sources.

OBJECTIVES: Using TransCad, define and build a transportation network starting with different source data types. Learn to use various TransCad network analysis tools.

DATA: (make sure you use only the data below for this part– check file names)

Story County Streets.dbd and related filesAmesDOQ.jpg and related file

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AmesTPLinks.txtAmes2000TAZx.dbd and related filesAnalysis Boundary.dbd and related filesData to be downloaded from the Iowa DOT

TASKS:

1) Convert a Tranplan network to a TransCad GIS line layer.2) Create a network line layer from the Story County Streets file.3) Use a DOT shapefile to create a line layer.4) Create centroid connectors.5) Add turn penalties and prohibitions.6) Check a line layer’s connectivity7) Calculate travel time8) Create a “network” from a line layer9) Use the network to create a shortest path matrix10) Use the shortest path tool to calculate shortest routes (via distance and travel time)

between two or more selected nodes.11) Use the Thematic Map feature to create a map that “effectively” illustrates

AADT.12) Use the TransCad “Create Bands” tool to develop a set of Isochronal time lines

from a specified node.13) Use the Traveling Salesman Routine to develop a path with fixed stops.

STEPS:

1) One way to create a base line layer for developing a network is to convert one from another travel demand modeling software program. In this step, a Tranplan network will be converted to TransCad. Note: for this example, the imported network will not overlay on any of the other layers, so do not be concerned about that for now.

a. From the Planning pull-down menu select the Import Planning Data>Import Planning Networks. (note: if the Planning menu option is not available, select Procedures-Planning to make it active)

b. Under the Import File Type select Tranplan and click the highway links button.

c. Select the AmesTPLinks.txt file and click Open. (This is a file that was exported from the Tranplan software program). Because the Tranplan network was provided in a different coordinate system, set the coordinate options as follows:

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d. Click OK and then assign a name for the new Standard Geographic File to be created (TRANPLAN) save it in your working folder.

e. This process now creates a GIS line layer file.f. Print a copy of the network to turn in. Label it “Tranplan Network”.

2) An alternative method to create a base line file for developing a network entails utilizing street files (such as those provided by Caliper Corporation with the TransCad software). The following steps utilize such a layer (TransCad streets file) to provide a base for a network.

a. Close TransCAD and open it again.b. Open the Standard Geographic Files named Story County Streets.dbd and

Analysis Boundary.dbdc. Create a selection set from Story County Streets.dbd to establish the links

needed for a model network. Use the polygon selection tool and quickly select a set of roads that comprise the Ames area or the overlay tools to clip out the roads within the analysis boundary.

d. Print a copy of the county roads layer as a background and highlight the selection set. Label it “Links to be Considered for Inclusion”

3) Iowa DOT data. a. The Iowa Department of Transportation has a variety of road data and a

complete network available for download on an MPO or county basis. The web address is:

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b. http://www.gis.dot.state.ia.us/ . Click on the “2006 Road, Structures …” link. Click on 2006. Download the 2006 Story County zip file. Go back up one level and click on the link called “metadata”. Metadata means “data about data” It tells you the contents and other information about the data files you downloaded. Save the metadata file for the road files (ROAD_INFO_SO_V.html) to your working folder for use later. Search the metadata html file for the text string “fedfunc” – this tells you the information about that particular attribute.

c. A look at the contents of the Story_2006.zip file reveals eleven shape files of the road and bridge network (.shp, .dbf, .shx, .prj). Note that each file has a .dbf data (attribute) file.

d. Extract the contents of the .zip file to your working folder. e. In the TransCAD File Open dialogue box, select ESRI Shapefile (*.shp)

from the Files of type: dropdown. Select Road_info.shp and left click on Open. The ESRI Shapefile dialogue box will open. The coordinates for this file are lat-long, so no conversion should be required. Click on the IMPORT LAYER check box which will let you create a new dbd file … call it road_info.dbd. Add AmesDOQ.jpg and Ames2000TAZx.dbd to your map.

f. We would like to join some information about the roads from other databases to our road_info layer. In this case, we are looking for files with the following fields:

Annual Average Daily Traffic (AADT) Federal Functional Class Speed Limit Length

The base files, road_info, has Federal Functional Class (FEDFUNC) as an attribute.

Note: following are the codes for the FFC field (you also found this information in the metadata)

The other attributes we are looking for exist in the following .dbf files:

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Direct_lane_2005.dbf Traffic_2005.dbf

g. Open these two files. Use File > Open, Files of Type: dBASE file (*.dbf) and each .dbf will appear in a Dataview. Also open a dataview to the road_info layer.

h. The file Direct_lane_2005.dbf has attributes for each road link in both directions for some links, which would complicate the joining of this database to the others. We just need information in one direction, so in the Direct_lane_2005 Dataview, use Selection > Select by Condition, and in the Enter a Condition text box, type DIRECTION <> “N” and then left click on OK. Choose EDIT-DELETE SET and say yes to permanently deleting these 533 records. Now chose “All Records” in the Records to

Display box i. Now you will join fields from the two dbase files to the story_roads layer.

Go to Dataview > Join. The Join dialogue box will appear. In the Joining From Table drop down, select road_info. In the to Table field, select Traffic_2005. Make sure the linking field for the data is MSLINK in both the Joining from Field and the to Field drop downs. Left click OK.

j. Repeat the previous step, adding Direct_lane_2005 to road_info+Traffic_2005. Each time in the Joining From Field box, choose roads_info:MSLINK and in the To Field box choose MSLINK. When complete, you should have a Dataview entitled Road_info +Traffic_2005+ Direct_lane_2005 and you will be able to use all the joined data fields in map building and querying (the joined dataview must be retained and open to do this.) Important: In order to save this joined dataview, you must export it.

k. After joining, use Dataset/Fields from the main menu, select column(s) which you do not want to see in the table and click on the Drop button (Figure 2). This way you will have only a few columns (AADT, Length, etc) in the dataview instead of many columns. Show these fields:

Road_info: MSLINK, FEDFUNC and NINEONEONE Direct_lane_2005: MSLINK, LIMITMPH Traffic_2005: MSLINK and AADT

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l. Back to the map … we don’t want all the lines as links in the model. To determine which roads to keep, make a thematic map (color theme – method: list of values) using the field Fedfunc (Federal Functional Class). Notice which roads have which values (create a legend to help you with this). Create a selection set of roads of functional class that you think are major enough to be included in the model (using a selection set). You will want to have the TAZs open as a background (not the editable) layer (Ames2000TAZx.dbd). As you’d like to keep roads from cutting through TAZs, remove from the selection set roads that go through TAZs. Also remove from the selection set the links outside the planning area. Save the selected set (tools-export-make sure you select standard geographic file) as a new dbd file called mynetworklines.

4) Create Centroids and Connectors. a. Close all open files and open Ames2000TAZx.dbd. Add

mynetworklines.dbd and AmesDOQ.jpg Use Map-Layers to rename the links layer from ROAD_INFO_2005 to mynetworklines.

b. Make the Ames2000TAZ layer the active layer.c. Go to Tools>Export and click the Export as Centroid Points check box

(saves a node at the center of each TAZ into a node file). Make sure you select Standard Geographic file format (the default is compact) and call it centroids.

d. Add your Centroid layer, rename the layer Centroids and make it active (if it is not already).

e. Use the TransCAD tools to automatically create centroid connecters (Planning>Planning Utilities>Centroid Connectors), setting the maximum number of centroid connectors to be 4 (default is 1) and choosing the mynetworklines file as the street file.

f. For zones 1-10 (labels using the TAZ field will help) use the network editing tool to modify their centroid connectors using rules we discussed in class and in the reading. Connectors should connect midblock, not at intersections. It will be helpful to note that the newly created centroid connector links have no MSLINK. Use that knowledge to recolor centroid connectors (create a selection set, MSLINK = null). The easiest way to

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change the centroid connectors is to delete them one at a time and add them back where they are supposed to be. In fact, so many of them need to be repositioned that you could just delete all of them in zones 1-10 and redraw them. You will want to look at the aerial photos to see where the TAZs have access.

g. Print a copy of your centroids, connectors, aerial photo and labeled TAZs in the area of 1-10. Label it properly.

5) Check Network Connectivity of mynetworklines: When you are editing a line layer you may want to check whether it is properly connected. Sometimes two nodes are on top of one another, the endpoints of lines have not been snapped to the same node, or a line is missing between two nearby nodes. Potential connectivity problems can be checked with the Tools-Map Editing-Check Line Layer Connectivity command, using a threshold of 5 meters. For each node, TransCAD lists all the nodes within the threshold distance, then ignores the nodes that are directly connected to this node by a line. If there are other nodes still on the list, this node is put into one of three selection sets, based on the number of lines connected to this node:

a. Level 1 contains nodes that have only one connected line b. Level 2 contains nodes that have two connected linesc. Level 3 contains nodes that have three or more connected lines

Each selection set has a distinctive style (you may have to pan around a bit to find one). By examining the selected nodes, you can focus on potential problems, then use the map editing tools to correct any problems. Using the same network file you have open, use the Network Connectivity Tool to analyze the connectivity. Describe (how many, where, what type) the problems you find in your network (if any) and discuss how you would fix them (even if you don’t have any).

6) Close all files and open the map with the saved joins to mynetworklines. Use the Color Theme Map Wizard to illustrate AADT volumes from the DOT. Pick colors which are intuitive for the viewer. Also increase line thickness for larger AADT values. Print a copy of the map to turn in.

7) Calculate travel time. a. Close all files and open the file you converted from TranPlan.b. Using the TranPlan network file make a new REAL column and edit-fill it

with an equation that calculates the link travel time using the speed and length. Speed (MPH) is located in the AB_Field_1 column and Length is in meters. Convert the units such that your formula results in minutes of travel time.

8) Turn penalties and prohibitions can be set for four types of actions: passing straight through an intersection, turning left, turning right, or making a U-turn (i.e., backtracking). Turn penalties can be set in three ways, and are applied in the following order:

a. Global turn penalties for the entire network. Global turn penalties are entered directly in the Network Settings dialog box.

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b. Link type turn penalties that apply between links of different types. These are to be stored in a table (using any of the formats that TransCAD supports) and can be displayed and edited in a dataview.

c. Specific turn penalties that apply between specific pairs of links. These are to be stored in a table (using any of the formats that TransCAD supports) and can be displayed and edited in a dataview.

d. Create global turn penalties to penalize all right turns by 0.2 minutes and all left turns by 0.4 minutes. You will need to create a network to do this:

i. select Networks/Paths> Create pull-down menu.ii. Select any fields (especially TIME) you would like to transfer to

your nodes or links in the new network file.iii. then select Network-Settings, turn radio button, turn penalties tab

and input your penaltiesiv. Click OK twicev. Assign a name to the new network file.

vi. Now notice in the bottom task bar there is a Network name visible. The name is present whenever a network file is open.

9) Create a shortest path matrix using the TranPlan network file. This tool is located under the Networks/Paths>Multiple Paths pull-down menu. Minimize on the travel time column you just created. What modeling functions are dependent upon the shortest path matrix (at least 4)?

10) Shortest Path Tool. This tool is valuable in checking the shortest travel path (via time or length) between any two or more nodes. Choose Networks/Paths> Shortest Path pull-down menu. Use the TransCad Help menu for specific instructions on how to use the Shortest Path Tool. Print an example of your use of this tool to be turned in. Compare a shortest time path with a shortest distance path. Describe three uses for this tool (a validation function, a user function, and a business or logistic function).

11) Use the Network Bands function to create Isochronal Time Lines based on Travel Time.

a. Make the nodes/intersections layer visible and hide the aerial photo.b. Select a node to base the timelines on.c. Select Networks/Paths> Network Bands pull-down menu.d. Base on travel time and selection.e. Print map to turn in (use a meaningful scale with enough detail).

Describe a good use for this tool.12) Use the Traveling Salesman tool to find a shortest route via various stops along a

network. a. Make a selection set of various nodes in different parts of the network.b. Select Networks/Paths> Traveling Salesman Problem.c. The stops are based on your selection set of nodes.d. Minimize Travel Time. e. Print map to turn in (use a meaningful scale with enough detail).

Describe a good use for this tool.

Report Format

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Submit a report with text answers to the imbedded questions and text descriptions of required figures. Number your figures and refer to them properly from the text. You may imbed the figures or attach them to the end of your file. Use good graphical communications techniques in your figures. Do not handwrite anything.

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