Which factor is used to compute capacity and LOS in signalized intersection analysis?

Which factor is used to compute capacity and LOS in signalized intersection analysis?

• A. Peak hour factor
• B. Cycle length
• C. Saturation flow rate
• D. Effective green time

Answer: (C)

How many vehicles can move through a signalized intersection is governed by how fast cars can discharge during a green phase, captured by the saturation flow rate. This rate represents the maximum discharge per lane under favorable conditions and serves as the fundamental capacity parameter. Capacity of an approach comes from combining that saturation flow rate with how much of the cycle is green (effective green time relative to the cycle length), and the Level of Service is then determined from the volume-to-capacity ratio. The other factors—cycle length and effective green time—shape how much of the cycle is available to move vehicles, and the peak hour factor affects how you estimate hourly demand, but they do not set the intrinsic capacity the way saturation flow rate does. Therefore, saturation flow rate is the factor used to compute capacity and LOS.

How many vehicles can move through a signalized intersection is governed by how fast cars can discharge during a green phase, captured by the saturation flow rate. This rate represents the maximum discharge per lane under favorable conditions and serves as the fundamental capacity parameter. Capacity of an approach comes from combining that saturation flow rate with how much of the cycle is green (effective green time relative to the cycle length), and the Level of Service is then determined from the volume-to-capacity ratio. The other factors—cycle length and effective green time—shape how much of the cycle is available to move vehicles, and the peak hour factor affects how you estimate hourly demand, but they do not set the intrinsic capacity the way saturation flow rate does. Therefore, saturation flow rate is the factor used to compute capacity and LOS.