  Bus Rapid Transit (BRT) systems can provide a fast and reliable service to
passengers at low investment costs compared to tram, metro and train systems.
Therefore, they can be of great value to attract more passengers to use public
transport. This paper thus focuses on the BRT investment problem: Which
segments of a single bus line should be upgraded such that the number of newly
attracted passengers is maximized? Motivated by the construction of a new BRT
line around Copenhagen, we consider a setting in which multiple parties are
responsible for the financing of different segments of the line. As each party
has a limited willingness to invest, we solve a bi-objective problem to
quantify the trade-off between the number of attracted passengers and the
investment budget. We model different problem variants: First, we consider two
potential passenger responses to upgrades on the line. Second, to prevent
scattered upgrades along the line, we consider different restrictions on the
number of upgraded connected components on the line. We propose an
epsilon-constraint-based algorithm to enumerate the complete set of
non-dominated points and investigate the complexity of this problem. Moreover,
we perform extensive numerical experiments on artificial instances and a case
study based on the BRT line around Copenhagen. Our results show that we can
generate the full Pareto front for real-life instances and that the resulting
trade-off between investment budget and attracted passengers depends both on
the origin-destination demand and on the passenger response to upgrades.
Moreover, we illustrate how the generated Pareto plots can assist decision
makers in selecting from a set of geographical route alternatives in our case
study.
