Conn. Agencies Regs. § 14-163c-4
Insofar as the provisions of subdivision (1) of section 14-163c-2 of the Regulations of Connecticut State Agencies apply to vehicles employed solely in intrastate use, the minimum age of an operator as stated 49 CFR Section 391.11(b) (I), shall be eighteen (18) years old in lieu of twenty-one (21) years old. This section shall not apply to the operators of any vehicles designed or used to transport more than fifteen (15) passengers, including the driver, or any school bus as defined in section 14-275 of the Connecticut General Statutes, or any vehicle that is used in the transportation of hazardous materials in a quantity such as to require the placarding of the vehicle under the Hazardous Materials Transportation Act, 49 USC App. Sections 1801-1813, inclusive, as amended from time to time.
Conn. Agencies Regs. § 14-163c-4