R.I. Gen. Laws § 39-12-12
It shall be the duty of every common carrier of property by motor vehicle to establish, observe, and enforce just, reasonable, and reasonably compensatory rates, charges, and classification, and reasonable regulations and practices relating thereto, which shall become effective on a date fixed by the carrier, which shall be at least thirty (30) days after the filing of the tariff containing the rates, charges, and classification, unless suspended by the administrator, prior to the effective date of the tariff or classification, upon complaint of any person, organization, or body politic or by the administrator on his or her own motion. No change shall be made in any rate, charge, classification, or any rule, regulation, or practice affecting the rate, charge, or classification, or the value of the service thereunder specified in any tariff of a common carrier by motor vehicle, except after thirty (30) days' notice of the proposed change filed and posted in accordance with § 39-12-11. The notice shall plainly state the changes proposed to be made and the time when the change will take effect. The administrator, in his or her discretion and for good cause shown, may allow the publication of rates or charges or a change in classification therein, upon notice less than that specified in this section, or may modify the requirements of this section with respect to the posting and filing of tariffs and classifications, either in particular instances or by general order applicable to special or peculiar circumstances or conditions. The administrator, after a hearing, may establish, from time to time, such reasonable rules and regulations as he or she may deem necessary pertaining to the form of tariffs, classifications, or supplements thereto; the time and manner of filing thereof; the suspension of rates before the rates become effective; and bearing upon the validity of any filed or existing rate. No common carrier of property by motor vehicle shall charge or demand or collect or receive a greater or less compensation for transportation or any service in connection therewith between points enumerated in the tariff than the rates and charges specified in the filed tariffs in effect at the time; and no carrier shall refund or remit in any manner or by any device, directly or indirectly, or through any other person, any portion of the rates or charges so specified, or extend to any person any privileges or facilities for transportation in intrastate commerce, except such as are specified in its tariffs.
R.I. Gen. Laws § 39-12-12