The first time I heard about traffic waves and the use of active feedback to eliminate traffic jams was from [Prof. John Mahoney](http://www.asap.unimelb.edu.au/bsparcs/aasmemoirs/mahony.htm) in 1984, he gave two 45 minute lectures on the subject and later in the year posed two related unsolved problems in the area on our exams, we were undergraduates at the time but that was typical of him to make up exams at the last minute and pack them with current problems from either current literature or his in-tray.