A critical measure of distribution logistics operating performance is transportation cost reduction. Transportation cost is the amount of money spent on moving products or materials from one location to another, such as from suppliers to warehouses, or from warehouses to customers1. Transportation cost reduction is the process of minimizing the transportation cost by optimizing the transportation modes, routes, frequencies, and capacities2. Transportation cost reduction can improve the distribution logistics operating performance by increasing the profitability, efficiency, and customer satisfaction of the distribution network34. The other options are not as critical or relevant as the correct answer. Part number rationalization is the process of reducing the number of different parts or components used in a product or a process, by standardizing, consolidating, or eliminating them5. It can improve the distribution logistics operating performance by simplifying the inventory management, reducing the inventory cost, and enhancing the quality and reliability of the product or process. However, it is not a direct measure of distribution logistics operating performance, but rather a design or engineering decision that affects the distribution logistics. Improved carrier selection is the process of choosing the best transportation service provider for a given shipment, based on criteria such as cost, speed, reliability, and availability. It can improve the distribution logistics operating performance by reducing the transportation cost, improving the delivery time, and ensuring the safety and security of the shipment. However, it is not a measure of distribution logistics operating performance, but rather a factor or input that affects the distribution logistics. Production lead time reduction is the process of decreasing the amount of time it takes to produce a product or a service, from the start of the production process to the end of the production process. It can improve the distribution logistics operating performance by reducing the inventory level, increasing the responsiveness to demand changes, and enhancing the customer satisfaction. However, it is not a measure of distribution logistics operating performance, but rather a measure of production or manufacturing operating performance.