A convertible ramp system facilitates transfer of personnel between spaced elevations. The ramp system includes a deck assembly, a convertible main ramp, and a convertible extension ramp. The convertible main ramp has a proximal end hinged to the deck assembly and a distal end adapted for being mechanically lifted and lowered relative to the deck assembly. Both the main ramp and the extension ramp incorporates an adjustable frame assembly and a series of simultaneously articulating foot treads carried by the frame assembly. The ramps are selectively convertible between a stairway configuration and a substantially flat and continuous runway configuration.