Circuity in the system is measured as the ratio of the total distance of flight segments to the direct distance between the origin and destination. Typically, non-stop flights have a circuity close to 1, indicating a direct route. Routes with low circuity are more efficient as they tend to have shorter flight times.
Figure 1 illustrates three categories of circuity: green for low circuity, blue for medium, and orange for high. The graph shows that allowable circuity is a decreasing function of the trip distance between origin and destination (O&D), suggesting that longer trips can tolerate higher circuity.
By default, the system assigns traffic factors of 0.5, 0.8, and 1.0 to itineraries with high, medium, and low circuity, respectively. This means that itineraries with high and medium circuity will capture only 50% and 80% of the potential traffic, respectively. Users have the flexibility to modify these factors within the range of 0.0 to 1.0. The traffic factor for low circuity is fixed at 1.0, indicating no penalty for itineraries in the green area below the low circuity curve in Figure 1.