Incremental network design with shortest paths

•We study the optimal choice and timing of network expansions.•We introduce a new class of incremental network design problems.•We develop a 4-approximation algorithm for incremental network design with shortest paths.•Analysis shows that coordinating timing of expansions increases the complexity of network design.

We introduce a class of incremental network design problems focused on investigating the optimal choice and timing of network expansions. We concentrate on an incremental network design problem with shortest paths. We investigate structural properties of optimal solutions, show that the simplest variant is NP-hard, analyze the worst-case performance of natural greedy heuristics, derive a 4-approximation algorithm, and conduct a small computational study.