Dispatching Continuous Moves
Ronen, David, Journal of Transportation Management
The term continuous move has emerged from the trucking industry during the last decade. A truck is productive (i.e., generates revenue) only when it moves loaded. From the truck operator=s perspective loading and unloading are necessary facilitating activities that rob truck time, whereas waiting and driving an empty truck are counter productive and should be minimized. Thus, the basic concept behind the term continuous move is that a truck should be kept moving with revenue generating loads. However, the term continuous moves has a variety of meanings depending on the type of operation with which it is associated. It usually refers to long-haul trucking operations where a truck is assigned several days of work and doesn=t necessarily return to its starting location. In order to keep their trucks moving loaded, truck operators give a variety of economic incentives to shippers (or to third party providers) who provide continuous moves for their trucks.
This paper reviews continuous moves (CM) in the context of a variety of operational environments. It introduces a classification of continuous moves, discusses the economic incentives offered by truck operators for continuous moves, presents a mathematical model that is used to construct and select an efficient set of continuous moves while simultaneously considering other feasible alternatives for dispatching the orders, and discusses practical considerations for implementing continuous moves. For the sake of clarity the next section provides definitions of commonly used terms, and defines and classifies CM=s. It is followed by a brief literature review of dispatching CM=s. Then, the orders dispatching environment is presented with a unifying mathe-matical optimization model that is used to dispatch orders. A discussion of practical considerations in dispatching CM=s follows, and we close with a brief summary.
CLASSIFICATION OF CONTINUOUS MOVES
In order to facilitate clear classification of continuous moves (CM=s), definitions of some basic common terms are required:
OriginB A single location (a stop).
DestinationB A single location (a stop).
OrderB A shipment from a single origin to a single destination with a size that does not exceed a truck=s capacity. If an order requires more than a truck= s capacity, it must be split into several orders.
LoadB The cargo on a truck at any given moment.
Truckload (TL) orderB An order that requires a full truck capacity or an order that is shipped separately on a truck (such an order may be a combined order consisting of several orders with a common origin and a common destination).
Inbound TLB A load on a truck consisting of several orders that have more than one origin, but a single destination. The intermediate origins are usually referred to as pick up locations.
Outbound TLB A load on a truck consisting of several orders that have a single origin and multiple destinations. The intermediate destinations are often referred to as stop-offs.
Less-than-Truckload (LTL) orderBAn order that requires less than a full truck capacity. Multiple such orders may be on a truck simultaneously.
Truck modeB A set of trucks that have the same operating rules and the same cost structure.
Truck typeB A set of trucks of the same mode that have the same physical characteristics (e.g., capacity, compartments).
The terms TL and LTL above correspond to a large extent to carriers= mode of operation and their freight rates.
Generally, a continuous move (CM) is a sequence of shipments (orders) assigned to a truck. However, not every sequence of shipments is a continuous move. For the purpose at hand a CM is defined as a truck route spanning more than one day and consists of a sequence of legs during which the truck is loaded (fully or partially) more than once, unloaded (fully or partially) more than once, and these activities are interwoven (all the loading activities do not precede all the unloading activities). …