Activities accessible by public transport

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10-01-2012 04:13 AM
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New Contributor
Hi there,
I would like to calculate how many different green space types (e.g. parks, playgrounds) are accessible by bus; cut-off value is 25min. I have 11 shape files with different types of green spaces (polygons). I created bus routes for each bus number. So my question is how can I calculate how many green spaces are in the accessibility range after commuting from each bus stop for 25min along every bus route?
Is Network Analyst Layer the right tool for this?
Vita
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Esri Regular Contributor
You will first need to convert the polygons into "points" to make them locations of a network. You can do this either by replacing them with a centroid location OR if the park/green space is big, find the intersections with all the roads around them.

Once you have these points, you can use the OD Cost Matrix solver (or the Closest Facility) and load your green spaces as Destinations and your bus stops as Origins and set a cutoff of 25 minutes and solve. The resulting Lines sub class will have the distances to every green space "destination" and you can Summerize this table to get number of locations per bus stop (origin).

If you need the shape of the actual paths taken then you can do the same with Closest Facility, loading the bus stops as incidents and green spaces as facilities and setting a cutoff as well as max number to find equal the the total number of facilities you loaded.

Jay Sandhu

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You could create a drive-time polygons (Service Area solver) by using the Network Analyst. Afterwards, you could perform spatial analysis in order to select those parks/playgrounds which are intersected by drive-time polygons.
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You will first need to convert the polygons into "points" to make them locations of a network. You can do this either by replacing them with a centroid location OR if the park/green space is big, find the intersections with all the roads around them.

Once you have these points, you can use the OD Cost Matrix solver (or the Closest Facility) and load your green spaces as Destinations and your bus stops as Origins and set a cutoff of 25 minutes and solve. The resulting Lines sub class will have the distances to every green space "destination" and you can Summerize this table to get number of locations per bus stop (origin).

If you need the shape of the actual paths taken then you can do the same with Closest Facility, loading the bus stops as incidents and green spaces as facilities and setting a cutoff as well as max number to find equal the the total number of facilities you loaded.

Jay Sandhu

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Thanks for fast answers! The closest facility works well. Since some of my green spaces are really big, I converted green space polygons into points with a combination of creating centroids, making intersections (thanks for that clue!) and adjusting Tolerance distance to facility locations.

I was wondering: would it be possible to restrain the routes to one interchange only (regardless if the max cut-off value is not met)? Would I need to set this up in the attributes of the route network or perhaps with The Closest Facility Barriers?

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I was wondering: would it be possible to restrain the routes to one interchange only


Not sure what that means. Can you describe what you want to achieve?

Jay Sandhu
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Hi,
sorry for not being clear enough.
So, I have routes of different bus numbers and I would like to find out how many different green spaces can one access from each bus stop with a cut-off value of 25min. This cut-off value is actually the whole travel time, not just traveling along the route. When I calculated The closest facility, some routes from incidents to facilities combine changing bus 3 or 4 times (which in reality means that commuting time extends to more than 25min). Is there perhaps a possibility of taking this into account? So that when a route from incident to facility demands changing bus, some more minutes would be added to the whole travel time? My only idea of how to do that would be to add interchange stops as barriers but then I don't know how that could be taken into account in order to achieve the 25min traveling time in whole.
hope this makes some sense.
vita
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Hello Vita.  It might be too late for your study, but I just wanted to let you know about a new prototype tool from Esri's Network Analyst team which allows you to add GTFS public transit data directly to a network dataset.  You can use this network dataset with the Network Analyst tools to run time-aware analyses that incorporate the transit schedules.

You could use this tool to run a service area analysis around your parks for many times of day to compare.  Unfortunately, we cannot currently limit the number of allowed transfers, so it's not a perfect solution yet.

You can download the toolset and instructions here:
http://www.arcgis.com/home/item.html?id=0fa52a75d9ba4abcad6b88bb6285fae1
Please do not hesitate to contact me at mmorang@esri.com with questions or comments about this toolset.
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