Problem with ArcGis 10.2 ans other questions

[Salma Sabour]

Hello,

First of all thank you for this excellent ArcGIS tool, I really want to try it in the modeling of new towns in Morocco. Only, I have a problem when I run the tool on Arcgis 10.2, I have an ArcGIS program bug and an ArcGis window crashes. I do not know at all what the problem is. This happens when I use the test files and the "Reach" measure.

Also I wanted to have information about how you can differentiate roads for cars, bicycles or pedestrians in the model.

Thank you a lot for your help

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Salma

[Andres]

Dear Salma,

Could you please send us the error message you are getting to cityform_rg[at]mit.edu and we can try to help you debug. 

To differentiate different travel modes, it would be easiest to input them as separate networks one by one, where you can set travel time as the impedance attribute according to the assumed speeds. If you want to have a multimodal network, that is possible too, but requires more work on preparing the network. You can take a look at ArcGIS online support multimodal networks for examples.

Andres

[Salma Sabour]

Dear Andres,

Thank you for your quick response. This is really encouraging for learning the tool. In fact I had no error, my ArcGIS program close unexpectedly without giving a name specific error, I reinstalled the ArcGis10 .1 and it works. So i will use the 10.1.

On the establishment of the network, could you tell me the most important elements of the attribute table required to use the UNA tool? are they available in the python script?

Otherwise you advise me to do a network for each track (automobile, bicycle and pedestrian), and change the specification in the speed attribute but I'm just a  beginner in ArcGIS and I do not know where to change it in the network attribute table. Thank you to inform me if you have time, otherwise I'll continue my research.

Thank you very much for your help

--
Salma

[Andres]

Dear Salma,

Glad it works now. I would suggest reading carefully the Help document, which should give you a sense of the attributes (http://cityform.mit.edu/files/UNA_help_v1_1.pdf). Generally, the most important attribute for the centrality metrics is "weights", which is essentially a numeric column in the input points file that describes the properties of the points (e.g. destination size, use, attractiveness etc.) that you want to use for weighing the analysis outcomes.

For setting up the network, the simplest way to start would be to set up your separate networks (see help for how to convert line networks to Network Datasets ND) and just use distance as the impedance attribute in each case, setting a different "Search Radius" in the UNA interface for different travel modes. If you have a pedestrian network, for instance, and want to compute accessibility in a 10min walking range, you may use 600m as your Search Radius (this assumes 3.6km/h average walking speed). Using a bicycle network as an input, and still modelling things in a 10min biking range, you may want to use a Search Radius of 1.67km (this assumes 10km/h average biking speed), etc.

Andres

[Salma Sabour]

Hello,

I have some questions about the modelisation of the ND to be accepted by the UNA model.

0. How to compute the accessibility in 10 min walking range, just using the search radius is not sufficient, is it?

1. Arrivals : how to simulate the arrival of workers in one hour in the buildings dedicated to the service activities ? The same for the departures.

2. How to draw the three kinds of paths ? What information should we have for each segment (number of lane, average speed, parking spaces on the right side of the lane, ...)

4. For the car paths, can we integrate different networks with different characteristics ? For instance : a primary network at 50km/h and a secondary network at 25km/h.

5. Can we integrate traffic lights ?

6. How the biking networks are characterized : number of bicycle lanes, average speed, maximum hourly flow rate ? What are the data required to determine whether a bicycle network will be saturated to or not ?

7. Same questions for the pedestrians.

If the response to my questions are in the making of a ND, can you give me a good internet site to do this :)

Thank a lot for your answer.

--
Salma

[Andres]

Hi Salma,

1. You can model accessibility in a 10min radius using the Search Radius, but it depends on your assumed mode of transportation -- 10min walking could be 600m, but 10min biking could be 2000m (assuming an avg speed of 12km/h).

2. Not sure what you mean by three types of paths? All cost attributes related to travel impedance in the analysis are hard coded to the network. If you want to model some edges as faster than others (assuming you are using "time" as impedance) then this will have to be hard coded to the network. For more on this, please see: http://resources.arcgis.com/en/help/main/10.1/index.html#//00470000000m000000

3. Yes, please see the link in the previous answer.

4. Yes, please see the link in answer 2.

5. Please see the link in answer 2. Note that the UNA toolbox will not be able to tell you about congestion on edges, it simple routes trips through edges. To model congestion, you would need to deal with a "max flow" problem using other tools.

6. See previous answer.

Best,

Andres