Transport and logistic sector is expected to obtain large benefits thanks to the implementation of 5G. This work proposes a framework based on 5G technology for Automated Truck Platoons (ATP) in urban areas to reduce energy consumption and Greenhouse Gas (GHG) emissions. More specifically, 5G features such as low latency communication (uRLLC), massive Machine Type Communication (mMTC) and enhanced mobile broadband (eMBB) are deployed with the Green Light Optimal Speed Advisory (GLOSA) to achieve the optimal speed of Automated Truck Platoons. The results of a preliminary test implemented in the Port of Hamburg show that 5G GLOSA ATP is promising in terms of energy consumption and GHG emissions reduction and increased truck platoon stability.