At approximately 4:37 P.M. the California Highway Patrol received a MAYDAY call of an aircraft that was down on SR 23 freeway southbound south of Tierra Rejada Road. Responding units came upon a small aircraft that was located in the number 2 and 3 lanes of the freeway. The pilot /instructor and flight student were standing outside the aircraft. The pilot informed officers he was having engine trouble and was unable to make it to the Camarillo airport. The pilot was able to land the plane safely on the freeway without hitting any vehicles or being struck by passing traffic. There were no injuries to the pilot and student. Officers assisted the pilot in pushing the downed aircraft into the center divider to clear the roadway. The Ventura County Fire Department and Ventura County Sheriff also responded to the scene. The FAA and NTSB were notified. The aircraft was originally out of the Van Nuys airport.