49 CFR § 375.705 - If a shipment is transported on more than one vehicle, what charges may I collect at delivery?
(a) At your discretion, you may do one of the following three things:
(1) You may defer the collection of all charges until you deliver the entire shipment.
(2) If you have determined the charges for the entire shipment, you may collect charges for the portion of the shipment tendered for delivery. You must determine the percentage of the charges for the entire shipment represented by the portion of the shipment tendered for delivery.
(3) If you cannot reasonably calculate the charges for the entire shipment, you must determine the charges for the portion of the shipment being delivered. You must collect this amount. The total charges you assess for the transportation of the separate portions of the shipment must not be more than the charges due for the entire shipment.