In this paper, we consider the uplink of a railway communication system with onboard mobile relays. Each onboard relay communicates with two cooperating base stations at the ends of the section along which the train is moving. Each carriage is equipped with two distinct antenna arrays. We design transmit coding schemes distributed between the antenna arrays and we apply receive macrodiversity. Simulations show that the proposed schemes enable to maintain transmission quality and throughput as the carriage moves along the section.