A truck assembly is configured to travel along a track having rails, and includes a first side frame, a second side frame, and a bolster extending between the first side frame and the second side frame. One or more of the first side frame, the second frame, or the bolster includes at least a portion formed as an I-beam that includes a web having a first end and a second end opposite from the first end, a first flange extending from the first end of the web, and a second flange extending from the second end of the web. A thickness of the web increases away from a first neutral axis towards the first flange and the second flange.