In one embodiment, an autonomous driving system perceives a driving environment surrounding an ADV based on sensor data obtained from various sensors, including identifying one or more objects. For each of the objects, an arc curve is generated connecting the object and a current location of the ADV using a predetermined algorithm. A curvature of the arc curve is calculated. One of the arc curves is selected in which the curvature of the selected arc curve satisfies a predetermined condition, such as the lowest curvature amongst all objects. A reference line is then generated by connecting the selected object and the current location of the ADV. The connected line between the selected object and the ADV is utilized as a part of a reference line. The reference line is utilized to generate a trajectory to drive the ADV.