Conn. Gen. Stat. § 14-262c

A tow dolly shall be exempt from the registration requirements of chapter 246. As used in this section “tow dolly” means a two-wheeled trailer without motive power (1) that is towed by a motor vehicle, (2) that is designed and used to tow another motor vehicle, and (3) upon which the front or rear wheels of the towed motor vehicle are mounted while the other wheels of the towed motor vehicle remain in contact with the ground.