运输密度又称“换算运输密度”。一定时期内平均每一营业千米运输线路所承担的换算周转量。货运密度或客运密度，只能从一个侧面反映运输线路（区段)运输能力的利用程度和运输工作强度。运输密度则能较全面地反映出运输能力的利用程度和运输工作强度，是确定新线建设和旧线技术改造计划的重要依据。
乙醇作为一种生物燃料相对来说容易生产。但是与汽油相比它的能量密度较低，而且不能够通过现有的化石燃料管线来运输。
As a biofuel, ethanol is relatively easy to make, but it has a lower energy density than gasoline and can't be transported through existing pipelines designed for petroleum fuels.
储有石油的地方相对较少，因其能量密度、泵送能力及在内燃机上的易用性使其特别适宜成为运输燃料。
Oil is found in relatively few places, and its energy density, pumpability and ease of use in internal-combustion engines makes it particularly well suited as a transportation fuel.
这些负面性质阻碍其使用，导致高运输成本，处理和储存困难以及低能量密度。
These negative qualities hinders its use because it results in high transport costs, difficulty in handling and storage, as well as low energy density.
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