Latest Contributions by MelindaMorang

Ack, sorry, I did some more experiments, and I now see that, in fact, you CAN do what I was suggesting.  You don't have to have a turn feature class with every turn digitized in to use a custom script evaluator for global turns.  It WILL work the way I originally suggested.  I think if you just fix your syntax, you should be good to go. In the mean time, I'll see what I can do about us getting some better documentation for this subject.  If I work here and can't figure it out, we clearly didn't do a very good job. ... View more

Hi Liam.  I'm afraid I was incorrect in my earlier post.  You can't actually use the default turn script evaluator effectively unless you have actual turn features drawn into your network.  If you are going to use this method, you will have to manually create all the turn features.  As you mentioned before, this would undoubtedly be quite laborious. As for why your code isn't working, it's a syntax problem.  In your if statements, you would need to use something like this: fromEdge.AttributeValueByName( "RoadClass" ) Also, you won't be able to just call "Economy" by itself.  That value is meaningless unless associated with a particular edge element.  As I mentioned before, you can't update the cost of the edge element itself based on the next edge in the route because the route doesn't know what the next edge is going to be.  The reason I suggested the turns is that turns are the only cost-associated element that has information about the edge elements it's connected to. So, unfortunately, this doesn't leave you with a lot of good options.  If you know ArcObjects, you could build your own custom evaluator, but this is not an easy process.  And, again, you can't use a custom evaluator to determine the cost of an edge based on the next edge in the route because the solver itself does not know what the next edge is going to be. I'm really sorry I don't have a better answer for you. ... View more

Okay, I think I've got it figured out. You want to create your own global turn script evaluator that will add a certain number of liters of fuel needed for each type of transition between road types (turn).  So, the fuel usage on the edges will stay the same as you have them now, but each transition between edges can add some value, based on the way you want to calculate it. First, when you create your network dataset, make sure you click the button that tells it you want to model global turns. Next, set up the global turn evaluator, as follows: - In the network dataset properties window, go to the Attributes tab. - For your fuel usage attribute, click Evaluators. - After the evaluators window pops up, go to the Default Values tab. - In the Type column next to Turn, click to get a drop-down menu where you can select "Script". - Click the Evaluator Properties button on the right (looks like a finger pointing at a piece of paper).  A dialog will appear where you can write a simple Python or VBScript that says how the solvers should calculate the fuel usage for turns in your network.  You should be able to use some if statements to give it a different value based on the road types of the fromEdge and toEdge. ... View more

Actually, I think you can use Global Turns for this.  Global Turns allow you to specify a different delay for turns between roads of different classes. http://resources.arcgis.com/en/help/main/10.1/index.html#//004700000030000000 ... View more

Hi Liam.  Unfortunately, the Network Analyst solvers don't have a way of assigning an added cost based on the previous edge traversed.  When the solver calculates the cost on an edge or junction, it doesn't know what the previous edge or junction was.  So you won't be able to do this automatically. You could potentially use a turn feature class to add your costs, but you would have to set up the turns manually for each intersection where you want the added cost. Can you describe more fully what you are trying to do?  What's the goal of this part of your project?  Maybe we can find a better way to do it so we can avoid this problem. ... View more

Thanks for the kind words, Jeremiah.  I'm glad to see that you were able to come up with a really nice solution for your project! We here at Esri are working to develop a much more advanced and useful set of tools for public transit analysis.  I am always interested in hearing from users working in this area to learn about their work, the types of analyses they want to perform, and the challenges they have with our current software.  Feel free to send me a private message if you want to talk further about public transit analyses.  You are also always welcome to contact me with complaints or suggestions about Network Analyst tools or documentation in general. Thanks, and good luck with your transit projects! ... View more

Unfortunately, there is not really a way to do what you are trying to do.  This is a difficult problem. As long as the impedance on both bus routes is exactly the same, the Network Analyst Route solver will somewhat arbitrarily choose which one to take.  We see this sometimes in cases where there are overlapping roads or loop-shaped roads where you could go either way around the loop.  However, if the impedances are exactly the same and the route segments are going to the exact same place, then the route generated will end up in the same place and show the same travel time, so the results will be "correct".  Unfortunately, if you are trying to generate directions, then you will see a difference in which bus it says to take. I wish I had a better answer. ... View more

You can do this by assigning values to the RouteName field in the Stops sublayer.  Each pair of stops needs its own, unique RouteName.  To make this easier to set up, I recommend doing this: - Add two fields to your input bus stop layer. - Populate one of these fields with the name of the stop. - Populate the other field with the name of the next stop. - Use Load Locations for the Route Stops sublayer TWICE so all your bus stops are put in twice.  Use field mapping each time to map the new fields you created to RouteName.  The first time you Load Locations, map it to the first field you created.  The second time, map it to the second field.  That way you end up with each pair of stops having a unique RouteName to themselves.  The solver will then solve a separate route between each pair of stops. ... View more

Please post the error message.  That will help us figure out what's wrong. ... View more

Hi Liam. When setting up your network dataset, you will need to set up some cost (impedance) attributes that determine how the network calculates the cost of each edge in the network when solving routes or other analyses. See http://resources.arcgis.com/en/help/main/10.1/index.html#/Understanding_network_attributes/00470000000m000000/. These cost attributes are calculated using evaluators.  You have many options (including code) for constructing an evaluator. See http://resources.arcgis.com/en/help/main/10.1/index.html#//00470000000n000000 for more information. For each attribute in your network, you can give it a different evaluator for the from-to direction and the to-from direction.  In other words, the cost of the same network element can be different if it's being traversed in different directions.  You will need to know the direction of digitization of your road to make sure you know which direction is which, but it should be easy enough for you to give each road a different cost if it's going uphill or downhill. ... View more

Hi Liam.  You've got yourself a challenging problem! Since you have elevation data, you can use the Interpolate Shape tool (http://resources.arcgis.com/en/help/main/10.1/index.html#//00q90000006m000000) to add z-elevation to the roads feature class in your network.  You could then calculate an average or maximum slope for each line feature and use this, as well as the 3D length, to calculate a new new cost attribute in your network dataset.  I'm not sure what advice to give you about how to construct your cost attribute.  Consider that each road segment may have some uphill and some downhill parts, some steep parts and some not-so-steep parts.  The average slope of the road feature might be zero even if it contains both a steep uphill part and a steep downhill part. Additionally, please note that you will likely encounter problems anywhere in your road network where you have bridges or tunnels, since your elevation data probably only accounts for the elevation at ground level.  If your data already had Z-levels for handling bridges and tunnels, you might be able to find a way to fudge the connectivity to make these work.  You might have to manually fix each one. ... View more

This sounds like a python question, so I have moved it to the python forum.  I hope you find your answer! ... View more

Hi Elizabeth.  Unfortunately, there is currently no way for the polygons to automatically keep a field from Facilities.  You have to first create the polygons and then do a join with Facilities using the Facility ID column in polygons and the Object ID column in Facilities. ... View more