Modeling the dynamic interaction of construction machines on loose terrain is essential for accurately predicting the vehicle's motion and for reliably conducting its operation. The track system is often exploited as the mobility for the construction machine the track shows high trafficability on loose terrain. Track-terrain interaction mechanics has been well investigated in the past, while that in steering motion of the track remains an open issue. Therefore, this research aims to clarify the interaction mechanics of the steering track on loose sand using the following experimental apparatus: an in-track sensor and a track-steering testbed. The in-track sensor possesses multiple small three-axis sensors on the track shoes. Each track shoe has multiple holes for the sensor such that the sensing position is selectable along with the track direction. This in-track sensor can measure the contact stress distribution generated between the track and loose sand. The steering testbed emulates a pivot turning of a tracked vehicle by offsetting the track at an arbitrary distance from the center of rotation of the steering testbed. The experiments using these two apparatuses reveal that the shear stress beneath the track shows a different tendency in its steering motion: the maximum shear stress of the towed track is generated at the center of the contact region while that of the driving track is at the front region. These observations can contribute to a better understanding of the steering motion of a construction machine on loose terrain.