Traffic capacity is associated with the solution of two mutually exclusive problems. On the one hand, it is impossible to increase the number of lanes in front road network (RN) junctions infinitely; on the other hand, in an attempt to increase the capacity of one of the directions, it is irrational to increase the cycle time of traffic lights, thus creating a problem for the conflicting direction. We have developed a method that allows us to determine with sufficient accuracy the duration of the green interval for a particular direction, depending on the traffic intensity on the busiest lane. The method takes into account time that allows the vehicle that was last in the queue waiting for the green light to complete the passage of the intersection when the traffic light changes from flashing green to yellow. Considering the process of changes in traffic intensity, reaching peak values, often in opposite directions at different times of the day, a need to preserve the capacity of an RN junction arises. This problem requires an increase in the number of traffic lanes in a particular direction in the area of the RN junction under consideration or an increase of the green interval for this direction. We have also determined the relationship between the number of lanes intended for traffic in a particular direction and the duration of the green interval for the same direction to make a compromise decision.