First, the original network G (N , A ) is transformed into a transshipment network GR (NR ,AR ) by eliminating the intersection nodes. Then, the network GR is transformed into a target network GE (NE ,AE ) by replacing every pickup & delivery node with a pair of pickup and delivery nodes. Eventually, the original routing problem defined on the G is converted into a routing problem defined on the GE that seeks to find the shortest Hamiltonian path from s to t satisfying the request of every (demand) node and the vehicle capacity constraints throughout the path