idleTransporters

The transporters this pool could send right now: allocated to nobody, and able to move.

Both halves are needed. A transporter halted by its movement gate part way through a repositioning move, or one under tow, belongs to nobody and is going nowhere; offering it is offering a vehicle that will not come. Worse, the default rule ranks candidates by distance to the pickup, and a stopped candidate is the one whose distance does not grow while the others' do -- so a blind rule does not merely include the stuck vehicle, it drifts toward it.

Use transporters for the whole fleet and haltedTransporters for the ones a gate is holding.