Module B2 - Slide 5

ModuleB2_Slide05

Some O&M instructors have mistakenly used “cycle” for “phase” (i.e., “not a long enough cycle for my student to cross”) or have used the terms interchangeably. It is important to know that traffic engineers have specific meanings for the terms. An interval is the time during which the signal does not change. Example intervals would be the green time for northbound through traffic or the yellow time for southbound left turning traffic. A phase is all intervals for a particular traffic movement, for example, the northbound traffic. A cycle is the sum total of all phases, for example, the time it takes from the beginning of the green time for northbound through traffic through the other phases and back to the beginning of the green for northbound through. A cycle length can be anywhere from one minute to several minutes.