By 2001 , four corridors had been studied as part of the plan : The Trans-Asian Railway Network Agreement is an agreement signed on 10 November 2006 , by seventeen Asian nations as part of a United Nations Economic and Social Commission for Asia and the Pacific ( UNESCAP ) effort to build a transcontinental railway network between Europe and Pacific ports in China .
By 2001 , the four corridors had been studied as part of the plan :