Often traditional mail carrier models assume that one carrier is assigned to each truck. This carrier drives the truck according to a delivery route, gets out of the truck at a stop, and services customers using a walking loop. We introduce the Paired Mail Carrier Problem (PMCP), which allows for two mail carriers per truck. If at least one carrier is in the truck, the truck may move forward. Given two mail carriers per truck, the objective is to minimize the time from the start to the end of the route while ensuring that each service stop is fully serviced and obeys all feasibility constraints. We develop a mixed integer programming (MIP) formulation and two fast heuristics for the PMCP. The MIP formulation obtains optimal solutions for smaller instances within reasonable running times. Furthermore, we demonstrate that, in addition to being very efficient (running time is on the order of milliseconds, even for large instances), our heuristics are near-optimal (within 5% of optimality) on instances up to 80 stops. More importantly, we evaluate the impact of the paired mail carrier (PMC) setting on both a one-truck situation and a fleet (multiple trucks) situation, relative to the single mail carrier (SMC) setting. Overall, the PMC setting not only can accomplish over 50% extra work within the same shift hours but also can lead to 22% cost savings. Finally, we discuss an extension where we can have three or more mail carriers per truck.

传统的邮递员模型通常假设为每辆卡车分配一个承运人。这家承运商根据送货路线驾驶卡车，在一站下车，并使用步行循环为客户提供服务。我们介绍配对邮递员问题 (PMCP)，它允许每辆卡车有两个邮递员。如果卡车中至少有一个运载工具，则卡车可以向前移动。给定每辆卡车有两个邮车，目标是最大限度地减少从路线开始到结束的时间，同时确保每个服务站都得到充分服务并遵守所有可行性约束。我们为 PMCP 开发了混合整数规划 (MIP) 公式和两种快速启发式算法。MIP 公式在合理的运行时间内为较小的实例获得最优解。此外，我们证明，除了非常高效（运行时间在毫秒级，即使对于大型实例也是如此），我们的启发式方法在最多 80 个停止点的实例上接近最优（最优性的 5% 以内）。更重要的是，相对于单一邮递员 (SMC) 设置，我们评估了配对邮递员 (PMC) 设置对单卡车情况和车队（多辆卡车）情况的影响。总体而言，PMC 设置不仅可以在相同班次时间内完成超过 50% 的额外工作，而且还可以节省 22% 的成本。最后，我们讨论了一种扩展，即每辆卡车可以配备三个或更多邮递员。相对于单一邮递员 (SMC) 设置，我们评估配对邮递员 (PMC) 设置对单卡车情况和车队（多辆卡车）情况的影响。总体而言，PMC 设置不仅可以在相同班次时间内完成超过 50% 的额外工作，而且还可以节省 22% 的成本。最后，我们讨论了一种扩展，即每辆卡车可以配备三个或更多邮递员。相对于单一邮递员 (SMC) 设置，我们评估配对邮递员 (PMC) 设置对单卡车情况和车队（多辆卡车）情况的影响。总体而言，PMC 设置不仅可以在相同班次时间内完成超过 50% 的额外工作，而且还可以节省 22% 的成本。最后，我们讨论了一种扩展，即每辆卡车可以配备三个或更多邮递员。