Service Area Analysis - Add turn out time

Question

I have done my service area analysis and the results look really good, however I need to a 30 second time window on the beginning of the run. The 30 seconds will represent the time from when the alarm rings to the time it takes the fire fighters to get the truck rolling out the door.

I'm in a pinch here, so hopefully get a quick response. In the meantime I'm looking online and reading help. I bet this is a simple setting somewhere.

Thanks in advance!

Melinda Morang · Answer

No, that is not the correct procedure. The Attr_ fields are in the Service Area layer. They are not built into the network dataset.

It sounds like you created your own network dataset. You should have created an Impedance attribute with some name, and perhaps the impedance values are being calculated using the Time field from your network dataset's source feature class. That's fine. The thing you care about is the name of the impedance attribute in the network dataset. Let's say it's called MyImpedance.

Now look at your Service Area layer and open the attribute table for the Facilities sublayer. You should see a field called Attr_MyImpedance. Put your value of 0.5 in there. (Assuming your impedance attribute has units of Minutes. If not, adjust the value for the correct units.)

Here is the correct documentation for a Service Area layer in ArcMap: https://desktop.arcgis.com/en/arcmap/latest/extensions/network-analyst/service-area.htm#GUID-23AFA603-CDB3-48A6-9E92-C5B0443CEC3E

Sean_Wray · Answer

@MelindaMorang I'm using ArcGIS Desktop and Network Analyst extension. In my road network I have a field called time where I have calculated the travel time for the speed limit assigned to the segment.

SO... Add a field to my network called Attr_Time and populate with .5 (for half a minute). Then rebuild my network dataset and rerun my analysis. Does that sound right?

Melinda Morang · Answer

I can't tell from your question how you are solving your Service Area analysis (using a layer in Pro? using Python arcpy.nax?), but you are correct that it's a simple setting.

For a Service Area layer in the Pro UI, you can use the "Attr_" prefix fields described here. The field name relates to the impedance attribute you're using in the analysis, so if your travel mode uses an impedance attribute called "TravelTime", the field name to add your turn out time to is "Attr_TravelTime".

For a Service Area analysis using the arcpy.nax solver objects, you can use the AdditionalTime, AdditionalDistance, or AdditionalCost field (depending on what you're optimizing - my guess is time). This is described here.