topic Re: Script evaluators element variables in ArcGIS Network Analyst Questions

Script evaluators element variables

sotokan80_ — Tue, 13 Feb 2018 12:49:41 GMT

In script evaluators how element variables work?

The following Element Variables are available:

Turn
fromEdge
atJunction
toEdge

Does "fromEdge" mean the previous edge and "toEdge" the next edge? Is there any documentation for Element Functions such as ToAzimuth, FromPositin, PositionAlongObject etc?

Re: Script evaluators element variables

PatrickStevens — Wed, 14 Feb 2018 22:20:00 GMT

The network element script evaluators are based on the ArcObjects API. To explain some of the sections of the dialog in your screenshot:

Element Variables: These are the objects that you can reference in the code block. For evaluating edges, the only valid element variable is the Edge element itself. In your screenshot, you see Turn, fromEdge, toEdge, and atJunction. These are all network elements associated with a Turn.

Types: This changes the available functions in the Element Functions section. For example, select Turn and you get the Angle function. Select Junction and you get the TurnCount function.

Element Functions: These are the methods available to work on the chosen element type object. These should correspond to the methods on INetworkEdge2, INetworkTurn2, and INetworkJunction2.

I hope this was helpful.

Re: Script evaluators element variables

sotokan80_ — Wed, 14 Feb 2018 22:52:59 GMT

Than you very much for your reply. I m trying to promote straight lines in my solver. Each street segment has a NON UNIQUE FID value. ie Richmond Avenue's street segments have FID value = 12345. Is it possible to write a script based on the following pseudocode?

a=fromEdge.AttributeValuebyName("FID")

b=toEdge.AttributeValuebyName("FID")

If a=b then dont turn

And what type of element should i use for that, turn or edge?And last but not least the edges and the junctions are evaluated based on what value(time, length)?

Re: Script evaluators element variables

PatrickStevens — Wed, 14 Feb 2018 23:51:45 GMT

If I understand correctly, you would like to discourage turns where possible. I don't think what you are proposing would work with the script evaluator.

I think some functionality that might do what you want is the Global Turn Delay Evaluator. The purpose of that evaluator is to discourage turns by applying a cost penalty that makes turning more expensive. That might be your answer.

To take a step back, though, why do you want to discourage turns? Is the vehicle that is travelling too big to make many turns? If that is the case, the Global Turn Delay Evaluator seems correct.

Or are you getting routes that leave major roads and stair-steps through communities? In this case, the best answer is probably to adjust the travel times along the roads that you prefer.