The paper introduces a local trajectory planner designed specifically for lateral guidance of autonomous vehicles. The inputs of the planner are the lane edges in the form of corner point coordinates in a two-dimensional plane. The aim of the planner is to provide a series of trajectory points ahead of the vehicle. The trajectory shall be well-conditioned which means no border violation (safety), no high lateral acceleration (comfort) and good tracking properties. The optimal conditions for driving have been found in using clothoid curves. The curvature of the clothoid is a linear function of the distance, which resolves the biggest disadvantage of circle conjunction: the discontinuity of the lateral acceleration. Clothoids have constant lateral jerk profile. In our work an Extended Kalman Filter is used with a clothoid model to consolidate inaccuracies of the lane detection system. The paper is presented as the first part of a research process. The algorithm introduced in this paper is planned to be continued with research on its automatized calibration procedures.