Abstract: A rail gauge measurement tool includes a frame mounting the tool to a rail vehicle, and an engagement unit that moves relative to the frame. The engagement unit has a first contacting element that maintains contact with a rail as the vehicle moves along a rail track, and a pair of parallel connecting shafts. The tool also includes an air cylinder exerting a biasing force so that the engagement unit maintains contact with the rail as the vehicle travels along the rail track. The tool also includes a linear sensor, separate from the air cylinder, that measures movement of the first rail engagement unit relative to the frame. The linear sensor and the air cylinder are parallel, but in a different plane from the parallel connecting shafts to lend structural support to the tool.