  Many networked systems involve multiple modes of transport. Such systems are
called multimodal, and examples include logistic networks, biomedical
phenomena, manufacturing process and telecommunication networks. Existing
techniques for determining optimal paths in multimodal networks have either
required heuristics or else application-specific constraints to obtain
tractable problems, removing the multimodal traits of the network during
analysis. In this paper weighted coloured--edge graphs are introduced to model
multimodal networks, where colours represent the modes of transportation.
Optimal paths are selected using a partial order that compares the weights in
each colour, resulting in a Pareto optimal set of shortest paths. This approach
is shown to be tractable through experimental analyses for random and real
multimodal networks without the need to apply heuristics or constraints.
