topic Re: I need to know how to create transfer junctions for a multimodal transportation network dataset in ArcGIS Network Analyst Questions

I need to know how to create transfer junctions for a multimodal transportation network dataset

DestinyKelley1 — Fri, 18 May 2018 22:11:35 GMT

I am a college student trying to create a multimodal network for MTA in New York City. However, I learned that having a NYC street feature class, a subway entrance feature class, a bus stop feature class, transit line routes and bus routes are not enough to create a working multimodal network. I need something called "transfer junctions" feature class(es) that connect these sources somehow before I can even begin to use network analyst's create a network wizard. I have read that transfer junctions are point features. I have searched online how to create them but there is nothing that is helpful anywhere.

How can I create these "transfer junctions" myself? Due to the volume of data that I have, manually using Editor to create them is not feasible for me. I need a tool in ArcMap that can generate them, and I see no such tool available in Network Analyst. I cannot believe ArcGIS's help doesn't explain this well at all. I am a novice at creating networks. Any help offered would be greatly appreciated! Thank you!

Re: I need to know how to create transfer junctions for a multimodal transportation network dataset

MelindaMorang — Fri, 18 May 2018 23:09:03 GMT

Hello Destiny.

I presume from your question that you have worked through the Creating a multimodal network dataset tutorial and are trying to replicate the network dataset structure with your own data. The network structure used in the tutorial data is just an example meant to explain how network connectivity works. It's not an "official" data model of any kind, so that's why you won't find any documentation about how to create "transfer junctions".

Before I dig into that data to remind myself what the transfer junctions do, let me ask you a clarification question: What is the goal of your project?

If you need to be able to use the public transit schedules in your analysis, the only way to do this is my creating a network dataset from your GTFS data using the Add GTFS to a Network Dataset tool. That tool allows you to solve your analysis for a specific time of day and uses the actual transit schedules to generate a result that is correct for that time.

The network in the tutorial does not use actual transit schedules. It just uses a simple travel time estimate on the subway lines that is not based on a schedule. Let me know if this is sufficient for your purposes, and I'll try to answer your original question.

[Asking because of my familiarity with your previous questions.]

Re: I need to know how to create transfer junctions for a multimodal transportation network dataset

DestinyKelley1 — Sat, 19 May 2018 00:26:54 GMT

Hi Melinda, thank you for answering my question. I don't think I need exact times and schedules per se. The average time it takes to get anywhere using Public Transit from my college is what I need. I am not considering time of day or day of the week specifically. I am trying to keep my results more simple and general.

Re: I need to know how to create transfer junctions for a multimodal transportation network dataset

MelindaMorang — Sat, 19 May 2018 00:41:11 GMT

I just looked at the tutorial data more closely, and now I realize that I don't know what you're asking. I'm not sure what a "transfer junction" is.

I'm guessing that what you need is a line feature connecting your station entrances and your stops. Is that right?

The Points to Line tool is useful for this. You will need to have pairs of points with a unique ID field so that a single line gets drawn to connect each stop with its appropriate station entrance. So you might have to do some work to get the data in the correct format.

If this is not your question, please clarify.

Also keep in mind that the available transit service changes significantly on different days of the week and times of day. You can estimate travel times, but the results of your analysis might not be very accurate at all. It's hard to define what a "simple and general" result for this type of analysis even is.

Re: I need to know how to create transfer junctions for a multimodal transportation network dataset

DestinyKelley1 — Sat, 19 May 2018 00:54:15 GMT

Perhaps then I should take into consideration the general times students would be most likely to travel to restaurants from the school, like say from 8am to 6pm, all days of the week since my school has weekend classes. I got the notion of transfer junctions from the following:

"A multimodal network requires multiple connectivity groups and the presence of transfer junctions in each connectivity group." Designing the network dataset—Help | ArcGIS Desktop

I am somewhat confused by what they are supposed to be and do for making the network.

Re: I need to know how to create transfer junctions for a multimodal transportation network dataset

MelindaMorang — Mon, 21 May 2018 15:17:43 GMT

A junction source feature can participate in multiple connectivity groups, unlike an edge source feature class. So, if you have two edge sources in different connectivity groups, you can assign a single junction source to be the "bridge" between the two connectivity groups by allowing it to participate in both groups. The junctions will represent the transfer points which are the only points where the traveler can transfer from one group (edge source) to another group (the other edge source).