Flat bed semi trailers are designed for transportation of heavy and bulky cargo on public roads. Platform semitrailers have reinforced frame, side members made from high-alloy steel welded on both sides, a moisture-resistant plywood floor, a reliable axle and suspension group and an efficient braking and lighting system. Capacity of such platform semitrailers depends on the quantity of axles and their capacities. Detachable steel or aluminum sideboards, container twist locks and stakes maybe assembled on flatbed semitrailers. Extension system is available for long and integral cargos. Lowered platforms maybe offered for over-height loads.