A recommendation system for multi-modal journey planning could be useful to travellers in making their journeys more efficient and pleasant, and to transport operators in encouraging travellers to make more effective use of infrastructure capacity.
Journeys will have multiple quantifiable attributes (e.g. time, cost, likelihood of getting a seat) and other attributes that we might infer indirectly (e.g. a pleasant view). Individual travellers will have different preferences that will affect the most appropriate recommendations. The recommendation system might build profiles for travellers, quantifying their preferences. These could be inferred indirectly, based on the information they provide, choices they make and feedback they give. These profiles might then be used to compare and rank different travel options.