DRIVER error was the cause of Monday's Aberdeen bus crash, police said yesterday after an examination of the vehicle's braking system found it to be working properly. A 14-year-old schoolboy was still in critical condition in Queen Mary Hospital last night. Eleven others were satisfactory. The Citybus double-decker went out of control and toppled over going down Shek Pai Wan Road. The 45-minute inspection was carried out yesterday morning by a Transport Department vehicle examiner, three engineers and technicians from Citybus and a police traffic accident investigator, Senior Inspector Lau Ho-sun. 'There was no apparent mechanical defect with the bus . . . and the braking system was working properly,' Inspector Lau said. Gauges on the air brake system showed there was very little pressure when the accident occurred. He said in the absence of any air leak, the only conclusion was the driver had her foot on the brake continuously, bleeding the system, but not enough to slow the bus. The Transport Department will implement new measures 'very soon' to ensure police are told when traffic lights are out of order, a senior official said. A bus driver was killed on Tuesday when two buses collided at Yen Chow and Un Chau streets in Shamshuipo after the traffic lights failed. Transport Department officials admitted they did not tell the police about the faulty lights.