物流谱系：首程、中段与末程

首程、中段和末程物流之间的区别在于单个货物的旅程。在整个旅程中，主要的运营目标是通过高效使用车队访问多个地点。考虑这样一个例子：一家制造商在典型的在线市场上销售商品，以触达个体消费者。

在首程和末程物流中，特定的货物从起点（首程中的工厂，末程中的配送中心）到终点（首程中的配送中心，末程中的客户）始终在同一辆车内运输。这些车辆路径问题（VRP）涉及在有限的时间内优化由几辆车组成的车队，通常是一天之内。优化的挑战本质上是分配和排序问题：确定哪辆车处理哪些货物组合，以及以何种顺序进行。

在我们的例子中，首程对应于收集制造商已售出的商品（例如 pofferts），而末程则涵盖最终交付给消费者的环节（其中一些消费者可能已经相当饿了！）。在这两种情况下，一辆卡车都将货物运往或运离区域配送中心。然而，如果制造商和消费者位于不同的地区，中段物流则连接了遥远的配送中心之间的空白。例如，来自荷兰格罗宁根（Groningen）的制造商的货物首先会运往乌得勒支（Utrecht）的区域配送中心，然后前往法国巴黎（Paris）的另一个配送中心，最后再交付给凡尔赛（Versailles）的消费者。

与首程和末程不同，中段物流更像是一场接力赛。单个货物可能在到达最终目的地之前，由多辆不同的车辆跨越大陆网络进行运输，这可能是在出发一周之后。在中间配送中心，货物可能会被卸下，按目的地分类，并与其他货运合并，然后装上下一辆车。这造成了一个复杂的同步问题：货物必须在特定的时间窗口内到达配送中心，以便赶上其预定的 outgoing 卡车。如果错过了预定的连接，它将在配送中心等待直到下一个周期，从而导致严重的延误。

在我们的例子中，一旦制造商的货物抵达乌得勒支区域中心，它们就会被装上第一辆开往安特卫普（Antwerp，比利时）的卡车，并在当天到达。由于前往巴黎的最紧迫的卡车已满，假设客户选择了标准运输，货物将在第二天从安特卫普乘坐第二辆卡车前往巴黎。包裹在第二天的夜晚抵达巴黎，随后进入末程网络，以便在第二天最终交付给客户。

The logistics spectrum: First, last and middle mile

The distinction between first-, middle- and last-mile logistics lies in the journey of an individual shipment. Throughout this journey, the primary operational goal is to efficiently use a fleet of vehicles to visit multiple locations. Consider the example of a manufacturer that sells goods on a typical online marketplace to reach individual consumers.

In first- and last-mile logistics, a specific shipment remains in a single vehicle from its origin (the factory in the first mile, the distribution center in the last mile) to its destination (the distribution center in the first mile, the customer in the last mile). These VRPs involve optimizing a fleet of several vehicles over a limited time span, usually a single day. The optimization challenge is essentially one of assignment and sequencing: determining which vehicle handles which set of shipments, and in what order.

In our example, the first mile corresponds to the collection of the items that have been sold by the manufacturer (e.g., pofferts ) while the last mile covers the final delivery to the consumers (some of them being quite hungry!). In both cases, a single truck transports goods to or from the regional distribution center. However, if the manufacturer and the consumer are in different regions, middle-mile logistics bridge the gap between far-away distribution centers. For instance, goods from a manufacturer in Groningen (Netherlands) would first move to the regional distribution center in Utrecht, travel to another center in Paris (France) before being delivered to a consumer in Versailles.

In contrast to the first and last mile, the middle mile functions as a relay race. A single shipment may be transported by several different vehicles across a continental network before reaching its final destination, maybe a week after departing. At intermediate distribution centers, the shipment may be unloaded, sorted by destination, and consolidated with other freight before being loaded onto the next vehicle. This creates a complex synchronization problem: the shipment must arrive at a distribution center within a specific time window to catch its scheduled outgoing truck. If it misses its scheduled connection, it will have to sit at the distribution center until the next cycle, leading to significant delays.

In our example, once the manufacturer’s goods arrive in the Utrecht regional center, they are loaded onto the first truck for Antwerp (Belgium) to arrive the same day. Because the most immediate truck to Paris is full, and let’s say the customer opted for standard shipping, the goods take the second truck the following day from Antwerp to Paris. The parcel arrives in Paris on the night of the second day, where it enters the last-mile network for the final delivery to the customer the next day.