Question About Azure Maps freeFlowSpeed

Admin GDOTTOPS 0 Reputation points
2026-09-16T20:48:36.98+00:00

Hello Azure Maps Support Team,

I am using the Azure Maps Traffic Flow Segment API and would like to better understand the freeFlowSpeed value returned by the API.

Could you please clarify how freeFlowSpeed is derived or calculated? For example, is it based on historical traffic observations, road attributes, or another methodology?

Any additional documentation on this field would be greatly appreciated.

Thank you

Azure Maps
Azure Maps

An Azure service that provides geospatial APIs to add maps, spatial analytics, and mobility solutions to apps.

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  1. AI answer

    2026-09-16T20:48:53.8833333+00:00

    freeFlowSpeed is the speed expected under ideal, free-flow conditions for that traffic segment, expressed in the units requested. It is directly related to freeFlowTravelTime, which is the travel time in seconds expected across the same segment under ideal free-flow conditions.

    Supported details for this field are:

    • getFreeFlowSpeed() returns: “The free flow speed expected under ideal conditions, expressed in the units requested.”
    • getFreeFlowTravelTime() returns: “The travel time in seconds, across this traffic segment, which would be expected under ideal free flow conditions.”
    • In Azure Maps traffic rendering, the relative traffic flow option compares current road speed against the road’s free-flow speed.

    The available documentation does not describe the internal derivation methodology for freeFlowSpeed beyond that definition. It does not state whether the value is calculated from historical observations, road attributes, or another specific model.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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  2. kagiyama yutaka 5,410 Reputation points
    2026-09-16T23:39:31.1933333+00:00

    I think freeFlowSpeed is the ideal free flow speed used in the TomTom and Azure Maps traffic model. It is not a measured speed and not tied to posted limits.

    Azure does not show how this baseline is calculated, and freeFlowSpeed is paired with freeFlowTravelTime because both come from the same baseline. The API gives this value as a reference to compare with currentSpeed or typicalSpeed to see how far conditions are from ideal.　

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