Trunk implementation plan for hierarchical networks

The Trunk Implementation Plan (TIP) is a multiyear schedule of planned trunk augments and disconnects that minimizes the impact of varying demand and forecast uncertainties on the cost of implementing a network meeting objective service criteria. This paper presents a theoretical development of the TIP algorithm for hierarchical networks that accounts for modularity, facility, and demand servicing constraints. First, we solve the only-route TIP problem analytically using stochastic dynamic programming techniques. We show that our analytical solution yields a numerically efficient algorithm for calculating a multiyear, minimum-cost policy. Second, we present the results of our analysis showing that, in the presence of forecast uncertainty, a near-optimal traffic network is obtained by introducing reserve capacity on the final trunk groups only. Based on this result, we construct the TIP algorithm for hierarchical networks by combining conventional network engineering principles with an optimal disconnect policy for high-usage trunk groups and the only-route TIP sizing procedure for final groups. Using this algorithm we obtain an economical multiyear schedule of trunk augments and disconnects for hierarchical networks.