How does the Service Area solver decide the width to stretch out from the lines of a network?

[Tsing-gan]

Hello all,

I'm looking for a way to explain how the various distances(as being measured in the figure) that make up service area were decided by the service area solver in ArcGIS Pro 3.2.1.

I failed to find any account of it in the esri help archive and have found no related descission here in the community. So I'm wondering if there's any way that I can check how the solver works, aspecially in this aspect, or access documents that might help me to figure it out?

Any answer helps to enrich my understanding to it(which is now "some algorithm did it") is appreciated!

Thanks in advance.

[Tsing-gan]

I want to say sorry for I didn't even noticed that "polygon trim distance" derictly decides the potential vertical distance of extent.

Now the following  observation leads me to another question.

The screenshot shown in the post was a result with default trim distance 100m. For most part of  the outcome area, the actuall distance of extension is far less then 100m, which I suppose may be resulting from some restriction against covering roads beyond cutoff distances. Now I want to know: what are the factors that may restrict trim distance or affect outcoming shape? And how does these restriction behave? For example, the restricted extension stops at different points from one segment of the network to another, how can I explain such seeming irregularity?

Thanks again.