Network Attribute Mappings - additional 'Road Class Value' required

[SimonLynch]

When configuring the Network Analyst network - Directions>Setting Directions>Attribute Mappings, there is a list of possible road class values, hard coded values within the NA software. For example road segments are classified as: Local roads (1); Highways (2); Ramps (3); etc and it even includes values for stairs, elevators sailing lines... to assist with Directions text.

It would be really useful if user defined values could be added to this list, and returned as part of the directions when a trace is performed. This would allow features along the network to be returned directly from a trace without having to do additional geoprocessing. Specifically, what we would like to do is to integrate bridges into the network, and know (sequentially) along the route where the bridges occur. So, for example, if a trace was done between two waypoints, we could then filter the list of directions, on the directions trace, to get a list of all bridges along the route and at what distance (from the start) they are encountered. The direction text / instruction could be something generic like "continue straight at bridge" - similar to what happens at roundabouts, where it says "continue straight at roundabout".

Adding these "features" as user defined classifications in the underlying network would be really powerful, as users could add whatever they want into the network - bridges, culverts, signs, ... it could even be applied to water networks, where sailors might sail under a bridge or through a lock.

A workaround that we are currently using is to (1) do the trace, then (2) do a spatial query using the resultant trace geometry, and (3) locate the selected features along the trace polyline - to get the distance from start. This is inefficient, and introduces complexities where bridges spatially intersect a trace but may be on an overpass for example and don't actually get crossed for that trace (route).

We have looked into the use of parameters to perform network analysis but this approach to parametrise restrictions - is insufficient because having the ability determine restrictions when restrictions are 'dynamic' in an ESRI Network would prove groundbreaking.

[LukePaine2]

Great idea!

[monmon]

User defined values would be great. Fantastic idea! 

[MelindaMorang]

Hello @SimonLynch. Thank you for your suggestion.

I am not entirely sure whether updating the Directions output is really the best way to solve your problem.  I have asked a colleague who's an expert in this area to have a look at your suggestion and share his thoughts.

In the meantime, I wonder if you have ever used the Copy Traversed Source Features tool and whether the output of this tool may serve your needs.  Essentially, you first solve a route, and you get a single feature showing the path taken.  Then, you run Copy Traversed Source Features, and it returns all the individual network edges, junctions, and turns that were traversed by the route, including the ObjectIDs of the features that were used.  Depending on how your network is modeled, this might directly give you the information you need, or you might be able to join this table with some attributes from your network source features to determine which bridges were traversed and in what order.

@LukePaine2 and @monmon, I would be interested to understand whether this would serve your needs as well or why you upvoted this idea (if you have some different use case).

[MelindaMorang]

Hi again.  I spoke to my colleague, and we have another suggestion that may also serve your needs.  If you include your bridges in a table of Reference Landmarks, you can retrieve the point locations and time along that route that each bridge was traversed from the DirectionPoints feature class created when directions are generated.

It's not clear from your question how you are performing the analysis, but the DirectionPoints output is available as a retrievable output type from the arcpy.nax solver objects.  For a network analysis layer, it can be found in the layer's analysis feature dataset where the data for the sublayers is stored.

If neither of the above suggestions (Copy Traversed Source Features or reference landmarks) give you what you need, we might consider adding support for specific new road class values, such as for bridges.  However, it's very unlikely that we would support any user-defined road class value, since we would not be able to determine what directions text should be used to properly describe traversal of that road class type.

[SimonLynch]

Hi Melinda, first of all thankyou for your response. It is difficult to know how much background & detail to put into these forums, for context, however:

We are attempting to leverage the potential within the ESRI Network for modelling a 'heavy vehicle access management system' in Tasmania (and potentially other jurisdictions in Australia). Bridges (short line segments in our network) are an access limitation for heavy vehicles (of many dimensions, configurations and classes). Hence our requirement to select for bridges, perform other bridge mass analyses on them, and incorporate these results through our Applications.

Your suggestion - of Reference Landmarks is something we had looked into but this wont work for our purpose. We looked at your suggested 'Copy Traversed Source Features' tool and it will reliably select bridges from our underlying Network features. Thanks for that suggestion! I think this kills off our request.

Thanks

[MelindaMorang]

Sounds great!  I'm glad Copy Traversed Source Features will give you what you need without any software changes, so I am closing this request as "Already Offered".

For those of you who upvoted this idea, if your needs are not met, please respond here to explain your use case.