using Network Analyst to dynamically model capacity

[JoshM_]

I've been playing around with Network Analyst (in 10.2) for the first time in a long time, never really had to use it much but I want to learn it some more.

I'm (think I'm) fine with the standard applications of it (routing, service areas). I'm curious if it has the functionality to do the following workflow.

Here's the setup/idea:

• assume a single road with multiple segments, let's pretend I split it into equal segments of 100 meters.


• each segment has varying capacity, defined by either lanes/width or a discrete number of people.


• all my cars start on the same point, and all of them are going to the same end point.


• imagine that halfway through the road, there's a toll booth. for this one segment, where speed/capacity slows down. if there's only one car on the road, it doesn't matter. if there are 1000 cars, it becomes a problem.

My question is: Can I get an output, showing increased time/costs to travel along each segment as I vary the amount of cars passing along the road?

That way, I could basically color-code the different segments for their level of service depending on different capacities. Maybe with one car on the road, everything is green. With 100, it's mostly green, red at the tollbooths and yellow just behind them. With 1000 cars, the red extends further back on the road.

I'm sure there are whole traffic modeling programs (Cube, TransCAD) that can do this, but I'd like to know if it could be done with just Network Analyst. Forgive me if this is really rudimentary.

Trying to search for anything ArcGIS with "flow" or "capacity" tends to yield a lot of ArcHydro stuff! I found ArcCASPER, but I'm not entirely sure if this is what I could use.

Full disclosure: I did post this on gis.stackexchange and gis.reddit as well, but so far no luck 😞

Thanks for any and all suggestions!

[RamB]

I can try for your question if you can clarify what you mean by "cars passing" and how will you get the number ? from external source/file ? I ask because NA is not dynamic in nature.

because basically what you are looking at is a v/c ratio. If you are getting v from a external source, then what remains is just a division of attributes. and then use symbology by proportion.

For just plotting exercise, I would recommend dynamic segmentation and linear referencing of arcgis.

[JoshM_]

Thanks for responding. Yes, I think I am looking for something dynamic in nature.

The "cars" would be population points from an external source. But instead of manually dividing them up or allocating them to each street on the network and manually calculating V/C, which is what I think you're suggesting, I would want to assign a start and end point on the route for the entire population, and see not just where V/C ratios are highest, but where they start to slow things down back in the system.

ArcCASPER has been great for this so far, but since it is based on evacuations, it can only get people moving away from points and to new points.

That is to say, it can do:

A, B -> C
but not
A <-> B

[RamB]

I do not think NA is a good place. You could, however to an extent, do this if you are good at programming with some assumptions.
You basically iterate shortest path while each segment load (volume or resistance) is fed back into the next shortest path calculation.

So no direct solution, I remember a group from denmark that made extensions for this but not free solution, its a traffic modelling package for arcgis. To an extent you could look at utility analyst, that helps in finding effects of a segment on upstream network.  Also not a very direct solution.

In short, dynamics is not the name of the game in NA.

** I am still not sure what is your end purpose, I can suggest some free tools outside arcgis if you like.

[JoshM_]

Don't have any programming skills, unfortunately.

I considered Utility Analyst but decided against it. I think it's because it also cannot do bi-directional flow (water only goes one way in a pipe!).

I would love the names of those extensions, whether they are free or paid! Thank you very much.

[RamB]

If you activiate your PM, i can send you the message, because I am not sure, If I can discuss external software here.