German legislation sets forth that anthropogenic greenhouse gases must be net-zero from 2045 onward (KSG, 2019). In contrast, road freight transport is projected to grow significantly (BMVBS, 2008; BMVI, 2021). If sustainable solutions for road freight transport are not implemented swiftly, Germany will not be able to meet its climate protection targets. This study analyzes the potential of the eHighway system-an overhead contact linebased electrification of trucks-to reduce the road freight transport's carbon footprint. Based on more than three years of field test operation with over 500,000 real-world driven kilometers, we estimate the saving potential of directly emitted greenhouse gases from five pilot overhead contact line trucks that use the eHighway system (Otrucks). We conclude that with only a five percent electrified stretch of a trip, 14-17% of direct greenhouse gas emissions are saved compared to a conventional truck. We develop a scaling and comparison calculator for the estimation of directly emitted greenhouse gases of O-trucks. We argue that with an electricity mix based upon renewable energies and an appropriately extended eHighway network, road freight transport is capable of offering transport with net-zero greenhouse gas emissions. Based on a unique data set, we provide a benchmark for all further research in evaluating eHighway technology and for comparing it to alternative drive technologies.