求翻译：运输一直被认为是对国家经济至关重要的，既要完成国家下达的客货运输任务，还要根据市场商品需求调节各自的运输，自身所创造的经济价值是十分可观的。是什么意思？

Transport has been considered critical to national economic, it is necessary to complete the national release of passenger and freight transportation tasks, also adjustable according to market demand for goods transport, their economic value is created by a very substantial.