R.I. Gen. Laws § 31-36-5: Measurement and marking of capacity of vehicles for transportation of fuels.

The capacity of every vehicle tank, and each compartment of it used for the transportation of fuels, shall be measured and sealed by an official sealer of weights and measures, and the capacity when so determined shall be plainly printed upon the right hand side of the vehicle tank in letters and numerals not less than one inch (1") in height.