Currently, the lost time of each stage is 4 seconds, and intersection critical v/c ratio is set to be 0.75 to avoid cycle failures caused by randomness of arrival traffic. Solve the following problems: 1) identify critical lane groups and solve their sum of flow ratios; 2) minimum cycle length and optimal cycle length; 3) Autonomous vehicle technologies make traffic movement at intersections more efficient. The lost time of each stage is reduced to 2 seconds, saturation headway is reduced by 10%. If the intersection demand does not change, calculate the critical v/c ratio corresponding to the minimum cycle length in 2).