Analysing truck-trailer-flatrack mix for a given road network with known supply and demand

Abstract

A flatrack is a modular, flat transport structure that can be seen as a larger version of a pallet. As compared to a pallet, a flatrack can accommodate a higher load volume and weight for transportation or storage, under specific supply and safety conditions. Their structure is durable, hence they can be reused many times like shipping containers. A loaded or empty flatrack must be carried by a truck or trailer for transportation from one location to another. The flatracks can be loaded onto a vehicle and unloaded from a vehicle together with its cargo via a mechanical arm integral to the vehicle. As such they act as a module to the trucks and trailers and facilitate rapid loading and unloading of cargo. We consider an organisation that intends to include flatracks in their vehicle fleet of trucks and trailers for transportation of cargo, from their own sources to destination locations, through specified road networks within given time windows. The loaded flatracks are unloaded (from the trucks and/or trailers) at their destinations as a single unit with their cargo, and as such they are not free for reuse until they have been emptied of cargo. This means that the flatracks may remain at the destination location for some time, and then the empty flatracks can be collected and returned to the source location for further use. A truck and trailer can carry multiple empty flatracks. Any delay in cargo removal from a flatrack and in empty flatrack collection may require the use of more flatracks in the system. On the other hand, frequent flatrack collection with partial vehicle loads might require more convoys to be operated. So a compromise between these two strategies is likely needed. The purpose of this research is to determine the number of flatracks required as part of a fleet composed of a given number of trucks and trailers, such that the fleet can adequately perform a set of predefined tasks. We have undertaken a simulation based study to analyse the performance of the system with three different flatrack recovery policies. Here, we assume there are adequate supplies at the supply nodes and the demands at the demand nodes are known in advance with their required time windows. Further the road network is fixed and given. With limited representative data, the simulation results show interesting insights that are useful for decision making.