Adjust walking time for slope in Network Analyst

[MartinDuffy49]

Hi all

I have a layer with 500 points and I'm trying to create surrounding polygons which are within 20 minutes walk of the point. The focus of this is older people walking to pharmacies. I have adjusted the walking speed downwards to 3.7 kms an hour  which is closer to the real walking speed of someone over 65. This works well for me in Network Analyst but I would like to further reduce or increase the speed depending on the slope which could have a substantial affect on the size of the polygon. I have attached a screenshot of the 20 minutes walk polygon based on the 3.7 walking time so you can see what I mean.

Is there any way to incorporate the slope also ? I have a dem and a slope map is needed. Thanks in advance.

[DavidPike]

I would run your slope analysis and break it into class breaks which define your estimated walking speed.

0-10% = 20% slower 

20-50% = 40% slower etc.

raster to polygon and set polygon values as 1.2, 1.4 .. (1.2 is 20% slower, 0.5 would be x2 faster - see doc below 'scaled polygon barrier')

https://pro.arcgis.com/en/pro-app/latest/help/analysis/networks/barriers.htm#:~:text=A%20restriction....

set the scaled polygon restriction and that should be it.

however this does not account for the downhill 'speed-up' you want to incorporate.  this is much trickier imho and really needs you to populate the network edges (paths) with to and from values in each possible direction.  You'd also need to first find the direction of the slope with the Aspect tool.  If your analysis can suffer not including downhill/uphill comparisons - I would definitely not go down that rabbit hole.  it may even be easier to produce some cost surface with a masked restriction to only include paths - again a technical rabbit hole.

[MartinDuffy49]

Much appreciated David thanks.

[MartinDuffy49]

I also should have mentioned it needs to be along the roads and footpaths that people can walk on rather than a general buffer

[DavidPike]

It doesn't matter.  The network drive-time areas/isochrones are only computed from paths along those routes regardless of restriction polygons outside of a viable route. 

You could clip the polygons by the roads/paths (with a small buffer distance), but it would very much be unnecessary for the analysis.