A reciprocating rod pumping unit includes a tower; a counterweight assembly movable along the tower; and a drum connected to an upper end of the tower and rotatable relative thereto. The unit also includes a belt having a first end connected to the counterweight assembly, extending over the drum, and having a second end connectable to a rod string. The unit further includes a prime mover for reciprocating the counterweight assembly along the tower; a sensor for detecting a condition of the pumping unit; a brake system for halting movement of the counterweight assembly; and a controller in communication with the at least one of the sensors and operable to activate the brake system in response to detection of the faulty condition of the pumping unit.