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An UNKNOWN transport operation is used when the shipment origin and destination are known, but the transport mode is not. TerraTwin tries a sequence of specific fallback transport modes in order, modeling each one in turn until a route can be calculated successfully.
Use an explicit transport type such as ROAD, RAIL, WATER, or AIR whenever the mode is known. An UNKNOWN operation uses defaulted mode configurations and may select a different mode than expected.

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Basic shape

Set the transport operation type to UNKNOWN:
In this example, the shipment travels from Shenzhen to Madrid, but the transport mode is not specified. That means TerraTwin treats the operation as UNKNOWN and tries specific fallback transport modes one by one. TerraTwin does not combine all of them or compare them all at once; instead, it attempts them in order and uses the first one that can be routed and calculated successfully.

Possible fallback transport modes for an UNKNOWN shipment from Shenzhen to Madrid.

For each fallback mode, TerraTwin uses a fully defaulted configuration. It stops as soon as one mode succeeds and returns the result for that mode. It does not calculate every mode or select the mode with the lowest emissions. If every fallback mode fails, the API returns the error from the final mode attempted.

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Properties

Mode-specific properties such as a vehicle, train type, vessel, or aircraft cannot be configured on an UNKNOWN operation. To control those details, select the transport mode explicitly.

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Omitting the transport chain

Leaving transportChain out of the request, or providing an empty array, has effectively the same calculation behavior as a single UNKNOWN operation:
Use an explicit UNKNOWN element when you want to provide an operation level id or context and have it returned with the corresponding result.

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Choosing the fallback order

By default, TerraTwin tries the following modes in order:
  1. ROAD
  2. WATER
  3. AIR
Use options.fallbackTransportModes to provide a different order:
In this example, TerraTwin attempts RAIL first, followed by ROAD, WATER, and AIR. The order matters: the first mode that succeeds is selected, even if a later mode would also be feasible. The supported fallback modes are AIR, RAIL, ROAD, and WATER.

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Recommendations

1

Use UNKNOWN only when the mode is genuinely unknown

Select a specific transport type when the shipment mode is available. This gives you control over mode specific parameters and produces a more deliberate calculation.
2

Order fallback modes deliberately

Put the most plausible or preferred mode first. TerraTwin stops at the first mode that can be routed and calculated successfully.
3

Provide enough cargo and location detail

Fallback operations use default mode configurations, but accurate cargo weight, category, and locations still improve vehicle selection, routing, and emissions results.