I teach at a school where the department has a strong expectation that a graduate or undergraduate course should require 45 hours of work per credit hour. For example, a 3-hour course should take 135 hours; say, 45 hours of lecture and the rest for readings and assignments. (The formal requirement is that 75% of students should be able to complete the work in that amount of time.)
At another school, the expectation for a class was 60 hours of work per credit hour. Furthermore, some professors took that requirement very seriously (including a time budget in the syllabus), whereas others took quite a cavalier attitude (“Do you want to be in graduate school or don't you?”). Of course, some classes take less than the allotted time.
At another school, I don't think I ever heard about a particular expectation, except perhaps an estimate of two hours of homework for one hour of lecture.
Given the range of variation, I wondered if there was any consistency of expectations across universities (say, in the United States, at the graduate and undergraduate level). Alternately, is there any pedagogical research that would inform either an instructor's or a department's policy about such matters?