One of the main concepts for improving the sustainability of supply chains is the collaboration between stakeholders by increasing the efficiency of their shared resources. In the literature, there are many research papers related to vertical collaboration in the logistics industry. However, horizontal collaboration has not received the same degree of attention. In fact, horizontal collaboration such as shared freight carrier and freight consolidation can also be considered vital for low-carbon supply chain solutions. In this paper, the problem of the design of supply chain transportation pooling strategies (SCTPS) is studied, which considers both vertical and horizontal collaboration. The purpose of this paper is to study the impact of these SCTPSs to reduce CO2 emissions using discrete-event simulation (DES)-based methodology. Using a numerical case study of two manufacturing companies and three customers, five SCTPS are studied including the following: (1) non-pooling strategy; (2) multi-pick strategy; (3) multi-drop strategy; (4) central hub strategy; and (5) combined hub and multi-drop strategy. The main result of the study is that all SCTPSs significantly reduce the CO2 emissions compared to the non-pooled supply chain. In fact, the reduction in CO2 emissions can reach 13% compared to the non-pooled strategy. Moreover, the best SCTPS that gives the minimum of CO2 is the hub strategy, followed by the multi-pick strategy and the multi-drop strategy.