Red light, green light: one teacher's variant on an old favorite [engineering education]

The author discusses a method of controlling the course delivery speed to engineering students. On the first day of class, the teacher hands out two pieces of paper-one red and one green. He then explains to the class that the red stands for STOP and the green for GO. The students are told that at any time during the term if they feel like the teacher is going too slowly they should simply wave a green sheet, if he is going too quickly, then wave a red sheet. No vocal signs are needed and no intelligent questions are required to get my attention.