The increasing demand for goods, especially in urban areas, together with the emerging information and technological advances are creating both opportunities and challenges for planning urban freight systems and improving their services. One of these promising opportunities is to use the underused assets in people transport systems (eg urban rail, buses or private-car trips) to transport goods [1]. As both people and goods move in the urban environment, a successful integration of their streams has the potential of enhancing the quality of their existing transportation services as well as reducing congestion and pollution levels [2]. For example, spare capacity in public transport systems can be used for retail store replenishment or a taxi can deliver freight when transporting a paseenger or during idle time. As this combination can lead to minimizing vehicle-miles traveled, it can also yield some transportation cost reductions for both passengers and freight.

This paper considers an integrated system in which a set of freight requests need to be delivered using a fleet of grounded robots where a public transportation service (referred to as scheduled line (SL)) can be used as part of a robot's journey1. This SL service is mainly used for transporting passengers and the idea of our model is to use this service for some freight deliveries when passengers demand is low. In other words, the model ensures that the potential transportation of freight does not distrub the transportation of passengers through the scheduled line. We thus consider that passengers and robots (carrying small parcels) share the same SL capacity where passenger demands are stochastic. Thus, depending on passenger demand realization, a robot might not be able to use the SL service and some recourse actions need to be applied. Thus, we develop a stochastic approach for operating this system and we perform an extensive computational study to analyze its performance and evaluate the impact of stochastic passengers demand on the overall cost of transporting freight through SL.