Link Tonnages

The tonnage summarized for each link by commodity and direction (upbound and down bound). The commodities include Coal, Petroleum Products, Chemicals, Crude Materials, Manufactured Goods, Farm Products, Machinery, Waste, and Unknown.按商品品类与通行方向（上行、下行）汇总各链路的货运吨位。本次数据集涵盖的商品品类包括煤炭、石油制品、化工品、未加工原材料、制成品、农产品、机械、废弃物及未知类别。