The article describes determined relationship between transport wireless network throughput and vehicle’s velocity. It is determined that such relationship is most precisely described by quadratic polynomial function, which was obtained by processing experimentally measured data and approximating them with various functions. When evaluating network's throughput with "application layer" and "transport layer" software, the highest layer overheads can be determined. As it was stated, they form a great part of transmitted traffic. It must be considered in practice, because network's throughput cannot be determined only by measurements of OSI Layer 3 or Layer 4 throughput.