OD Matrix cost (time) and transfers

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01-04-2019 09:18 AM
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OrlandoAndrade_Barraza
New Contributor

Hello Melinda, thanks for your contributions. I have a doubt that I hope you can help me. There is a video that you uploaded called:  Travel TimeBetweenPoints. Which in  some sense is the grade of accessibility that gives a  particular transit network.

 

You set up the transit network data set from the GTFS.  When you use the tool OD matrix cost to estimate the time spend from   given point to several destinations arcgis is taking in consideration the transfers? If so it   gives  the optimal route to the destination taking in consideration this transfer?  Because  in many situations there is not way  that from a origin to  many destination you can reach it with just 1 line.  And if argis is taking in consideration the transfer , it adds the  waiting time of the other line  (given by the headway) ?

On the other hand, unfortunately in my city there is not GTFS yet  (we are building it) I see in all cases that in order to create the transit network dataset to analyze  the data  the  software always use GTFS.  Do you know if there is some way to only use shapes?

 

Thank you.

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MelindaMorang
Esri Regular Contributor

Hello Orlando.

Yes, when you do network analysis (OD Cost Matrix, Route, etc.) with a GTFS-enabled Network Dataset created using the Add GTFS to a Network Dataset toolbox, the full schedule information for the transit system is used.  The network includes the transit and the streets, and it automatically handles transfers between lines by allowing the traveler to walk along the streets to make connections between one bus and another, for instance.  The transit schedules are used, so the wait times are automatically included in the analysis.

The tools calculate the optimal route by finding the shortest travel time between two points.  Unfortunately, the routes chosen do not always reflect the "best" route in reality.  The results may include a very large number of transfers (which most travelers will not do) or a longer walking time than most travelers would be willing to do.  There is no way to limit the number of transfers or the overall walking time, unfortunately.  This is a limitation of Network Analyst itself.

The Add GTFS to a Network Dataset tool requires GTFS data as an input.  It can't work with just the line shapes because then the schedule information couldn't be used to create accurate travel time estimates.

If you don't care about the schedules and the travel times for some reason, you could use just the shapes to create a network dataset as described in this tutorial.

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MelindaMorang
Esri Regular Contributor

Hello Orlando.

Yes, when you do network analysis (OD Cost Matrix, Route, etc.) with a GTFS-enabled Network Dataset created using the Add GTFS to a Network Dataset toolbox, the full schedule information for the transit system is used.  The network includes the transit and the streets, and it automatically handles transfers between lines by allowing the traveler to walk along the streets to make connections between one bus and another, for instance.  The transit schedules are used, so the wait times are automatically included in the analysis.

The tools calculate the optimal route by finding the shortest travel time between two points.  Unfortunately, the routes chosen do not always reflect the "best" route in reality.  The results may include a very large number of transfers (which most travelers will not do) or a longer walking time than most travelers would be willing to do.  There is no way to limit the number of transfers or the overall walking time, unfortunately.  This is a limitation of Network Analyst itself.

The Add GTFS to a Network Dataset tool requires GTFS data as an input.  It can't work with just the line shapes because then the schedule information couldn't be used to create accurate travel time estimates.

If you don't care about the schedules and the travel times for some reason, you could use just the shapes to create a network dataset as described in this tutorial.

View solution in original post

OrlandoAndrade_Barraza
New Contributor

Hello Melinda

I really appreciate your quick answer.

Thank you

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