[Solution Shown Below]
Webster's optimum cycle length equation, which is shown below, has two variables on the right-hand side. These are the total cycle lost time (L) which is usually taken as the sum of all the intergreen times, and the sum of all the critical flow ratios (S(V/s)).Co= 1.5L + 5
1 - S (V/s) In this case, the sum of the intergreen period lengths is 17 seconds (L=17). The sum of the critical flow ratios is 0.619. When we substitute these values into the equation above we obtain an optimum cycle length of 80 seconds. If all of the critical flow ratios were very near zero, the denominator in Webster's equation would approach unity and the optimum cycle length would be 31 seconds.