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"Fixed Speeds" for countries using Network Analysis

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10-13-2023 07:32 AM
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MarkThomas
Emerging Contributor

When creating service areas and generating drive time areas in ArcGIS Pro (using the ArcGIS Online routing service), there's a table in the online documentation that indicates the "Speed Data Source" for each country.  One of the values is "Fixed Speeds," defined in the Arc Online documentation as having "Comprehensive street data with static travel times derived from historical average speeds for automobiles is available. Analysis results won't vary by changing the time of day."  Does this mean that for countries with Fixed Speeds indicated, that all streets/roads in the entire country are categorized the same? That is, there aren't fast intercity roads and slow local roads, fast paved roads, and slow unpaved ones, etc?   Just all are the same?  The alternative would maybe be if the static speeds are assigned to each road; these don't change by time of day, but maybe different roads do have different values. But I don't see that this degree of granularity is available within the service area layer. The country of interest is Tanzania.

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DavidSolari
Frequent Contributor

Based solely on the quoted passage, I'd assume each path segment in the network has a fixed impedance that can vary per segment. If you want to confirm this, run several routes with various types of paths (e.g. only highway, then only local roads, then local to highway to local etc.) and graph the travel times vs distance for each route. If every route has the same impedance then you'll get a linear correlation between distance and time, if not then you won't.

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