The transportation of a truss-spar hull from a transport barge of 6000 ton topside module on the spar hull is investigated in the present study. Two possible routes from a fabrication yard in Teeside, England to the Gulf of Mexico are considered in the paper. The results of motion responses of the transport barge obtained from a spectral analysis and the limiting criteria of sea fastening, deck wetness and lateral acceleration are compared and the route selection is discussed. Long-crested waves and short-crested seas as well as the joint probabilities of significant wave heights and wave periods in different sea areas are considered. Generally speaking, the results for long-crested seas are higher than those for short-crested waves.