Are drug DUI penalties harsher than alcohol DUI in Rhode Island?

Often, yes. A conviction for being under the influence of a drug is sentenced in the same tier as a BAC of 0.15 or higher under § 31-27-2(d)(1)(iii), (d)(2)(ii), and (d)(3)(ii). In a drug-only case, the judge can substitute blood and urine testing for the interlock under § 31-27-2(d)(9). The other differences are evidentiary (no per se threshold for drugs, different test methods).