Network Analyst Restrictions

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05-14-2018 03:54 PM
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New Contributor III

I'm trying to find a proper definition for "Non-routeable segments" within the Layer Properties. I have a general idea of the meaning and I've seen some websites mentioning it, but nothing definitive. Can anyone help me out with the difference between "routable" and "non-routable" roadway segments?

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Esri Regular Contributor

Basically it's whether a piece of road can be traveled on or not.  So, if a stretch of road has a restriction attribute marking it as restricted for trucks carrying hazmats, then this stretch of road is non-routable for trucks carrying hazmats.  Those trucks will have to find another way.  But it might still be routable for ordinary trucks and cars.

Is there a particular place in the documentation where you found this that's confusing you?  If so, please leave a link, and we can look at clarifying it.

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Esri Regular Contributor

Basically it's whether a piece of road can be traveled on or not.  So, if a stretch of road has a restriction attribute marking it as restricted for trucks carrying hazmats, then this stretch of road is non-routable for trucks carrying hazmats.  Those trucks will have to find another way.  But it might still be routable for ordinary trucks and cars.

Is there a particular place in the documentation where you found this that's confusing you?  If so, please leave a link, and we can look at clarifying it.

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New Contributor III

Not particularly confusing, I'm just trying to explain it to a non-GIS user and was hoping to find a website with a clear definition to point her to. But you confirmed my self-made definition so that's helpful! Thank you!

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Esri Regular Contributor

Maybe this documentation page section will be helpful: Understanding network attributes—Help | ArcGIS Desktop 

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New Contributor III

Ok yes, that’s helpful. Thanks!

On a somewhat related note, when traveling along the network dataset to get the distance from one point to another, when it stops at the end point, it stops right in front of the point on that road, correct? Assuming there are no restrictions. So if there was a parking lot or a large amount of space between the road and the end point, it would still end on that road (it wouldn’t take you right to the point if there was no underlying road). Does that make sense? Is that correct?

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Esri Regular Contributor

Yes, that's correct.  When you add/load locations to your NA layer, the original points must "locate on" the network dataset.  This means that their original lat/lon location must snap to the closest part of the network, and this snapped location is considered the starting and ending point of the analysis.  If you want to model a parking lot or a long driveway, you need to include that as part of your network dataset.  Alternatively, for each location, you can set an added cost value using the Attr_[Impedance] field in the attribute table, where [Impedance] represents the name of the impedance attribute you're using for the analysis.  So if you know it takes an extra 5 minutes to get to your stop from the curbside, and your impedance attribute is called TravelTime, you can put a value of 5 in the Attr_TravelTime field in the attribute table for your Stops sublayer (assuming you're solving a Route).