where dij is the network distance between any pair of centres, i and j. Figure 3.5 shows two possible outcomes. If the triangle formed by three centres has no angle greater than equal to 120°, then the optimum location for the junction or is that point where the radial routes to each centre form three angles of 120° (Figure 3.5A). If contains angle greater than 120° the optimal the triangle an location for the junction is at that vertex (Figure 3.5B).