One of the most important capabilities expected from an autonomous vehicle is avoiding collision with obstacles in its path. For this purpose, autonomous vehicle must be able to perform an emergency maneuver as soon as the obstacle is detected. This paper presents a method for designing and performing an emergency maneuver in order to avoid collision with a fixed or moving obstacle in the path. A sinusoidal or exponential trajectory, which is a function of the relative distance between vehicle and obstacle, is designed as the desired trajectory for lateral motion of the vehicle. A sliding mode controller is designed in order to guarantee that the vehicle tracks that desired trajectory. The method does not have computational difficulties and is appropriate for real time implementations. A virtual test environment for evaluating the performance of the system has been prepared using Matlab/Simulink and ADAMS/Car software. A full vehicle model, validated by experimental tests, is used as the autonomous vehicle model in ADAMS/Car