46 C.F.R. § 520.12 – Time/Volume rates.

(a) General. Common carriers or conferences may publish in their tariffs rates which are conditioned upon the receipt of a specified aggregate volume of cargo or aggregate freight revenue over a specified period of time.
(b) Publication requirements.
1. (1) All rates, charges, classifications rules and practices concerning time/volume rates must be set forth in the carrier's or conference's tariff.
2. (2) The tariff shall identify:
  1. (i) The shipment records that will be maintained to support the rate; and
  2. (ii) The method to be used by shippers giving notice of their intention to use a time/volume rate prior to tendering any shipments under the time/volume arrangement.
(c) Accepted rates. Once a time/volume rate is accepted by one shipper, it shall remain in effect for the time specified, without amendment. If no shipper gives notice within 30 days of publication, the time/volume rate may be canceled.
(d) Records. Shipper notices and shipment records supporting a time/volume rate shall be maintained by the offering carrier or conference for at least 5 years after a shipper's use of a time/volume rate has ended.
(e) Liquidated damages. Time/volume rates may not impose or attempt to impose liquidated damages on any shipper that moves cargo under the rate. Carriers and agreements shall rerate cargo moved at the applicable tariff rate, if a shipper fails to meet the requirements of the time/volume offer.