The traffic capacity of the merging area where a ramp enters the mainline is primarily affected by the traffic capacity of the downstream mainline section, while the traffic capacity of the diverging area where a ramp exits the mainline is mainly constrained by the traffic capacity of the off-ramp itself. Evaluating the traffic capacity and service level of merging and diverging affected areas can effectively reflect the operational status of these areas. Currently, there are no comprehensive domestic standards detailing the evaluation methods for these affected areas. The calculation is conducted according to the relevant provisions and methods in the Road Capacity Manual of the United States (abbreviated as HCM2000 Manual, by the American Transportation Research Council). The design and checking computation are carried out by calculating the traffic density, ramp flow rate and the maximum flow rate in the affected area, and based on the predicted traffic flow for the near-term (2031), medium-term (2041), and long-term (2051) stages. The research results indicate that all merging and diverging areas meet the requirements of service level under the designed scale without congestion observed.