transit network dataset modified to include walking; walking results erroneous

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02-20-2021 03:25 PM
psimon
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New Contributor

Hello!

I have created a GTFS network dataset and it has worked well for me to do public transit analysis. What I wanted to also determine is how many bus stops are within 15 min walking distance as well as travel time by walking between locations.

I modified the existing Transit Network dataset to include walking as travel mode, but for some reason it produces erroneous results. I cannot seem to find the cause for this and would appreciate your advice.

I have posted the dataset at this link if anyone is interested: https://arcg.is/1rv4nf

Many thanks in advance,

Patrick

 

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MelindaMorang
Esri Regular Contributor

Hello Patrick.

I looked at your network, and I think I know what the problem is. The WalkTime cost attribute included in the network by default (created from the provided template) is not really meant to be used to model walking only. I realize this is a bit misleading. Essentially it is there to help create a reasonable walk time estimate for use in the transit calculations and so you can accumulate the total walking time used in your transit journeys. For this reason, it calculates the walk time along transit lines (LineVariantElements) and StopConnectors as 0. If you use the WalkTime cost attribute directly, it sees the transit lines as free to use, so your routes will be all weird.

If you want to use this network to model walking, you can do one of two things.

1) Cheat. Use your transit travel mode, but just don't set a time of day. The transit lines will never have any service and will be effectively restricted, and so all calculations will default back to walking.

2) Continue along the route you're currently on, but fix your walking travel mode. The easiest thing is to create a restriction attribute that makes LineVariantElements and StopConnectors restricted all the time and make sure this restriction is turned on for your Walking travel mode.

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2 Replies
MelindaMorang
Esri Regular Contributor

Hello Patrick.

I looked at your network, and I think I know what the problem is. The WalkTime cost attribute included in the network by default (created from the provided template) is not really meant to be used to model walking only. I realize this is a bit misleading. Essentially it is there to help create a reasonable walk time estimate for use in the transit calculations and so you can accumulate the total walking time used in your transit journeys. For this reason, it calculates the walk time along transit lines (LineVariantElements) and StopConnectors as 0. If you use the WalkTime cost attribute directly, it sees the transit lines as free to use, so your routes will be all weird.

If you want to use this network to model walking, you can do one of two things.

1) Cheat. Use your transit travel mode, but just don't set a time of day. The transit lines will never have any service and will be effectively restricted, and so all calculations will default back to walking.

2) Continue along the route you're currently on, but fix your walking travel mode. The easiest thing is to create a restriction attribute that makes LineVariantElements and StopConnectors restricted all the time and make sure this restriction is turned on for your Walking travel mode.

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psimon
by
New Contributor

Thank you very much Melinda for taking the time to review this and your helpful advice!

To confirm for any future readers, I tried both of the options and they both resulted in correct estimates.

Patrick

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