Design Process Outline This page is meant to guide you through the design process. Knowing a little more about how these various concepts are used together will make the individual concepts easier to understand. Pre-Design Data Collection: The design of signal timing schemes is a fairly simple, though multi-step process. First, you need to know most of the roadway conditions surrounding the intersection you are working on. This includes the number of lanes, the width of the lanes, the width of the intersection, the width of the shoulders, and more. Second, you need to have information regarding the composition of the traffic, such as the percentage of busses and the percentage of trucks within the traffic stream. You also need to know the peak hour volumes and peak fifteen-minute volumes for all of the various movements. The Design Process: The basic steps in the design process (assuming you are using Webster's method – see Cycle Length Determination module) are listed below. While this particular listing is oriented toward Webster's method, most of the other methods incorporate the same concepts, but in a slightly different way. Decide on a phasing plan. Calculate the length of the intergreen period for each phase of your cycle. Calculate the minimum green time for each phase based on the pedestrian crossing time. Calculate or measure the saturation flow rate for each approach or lane. Calculate the design flow rate for each approach or lane using the peak hour volume and peak hour factor. Find the critical movements or lanes, and calculate the critical flow ratios.    Calculate the optimum cycle length. Allocate the available green time using the critical flow ratios from step six. Calculate the capacity of the intersection approaches or lanes. Check the capacities/design flow rates and green intervals/minimum green intervals. Adjust your cycle timing scheme if necessary. Even though this outline is tailored for Webster's method, you'll find that most of the other design methods involve many of the same calculations. Refer to this roadmap frequently as you proceed through this chapter, so that you can see how each calculation is related to the design process.