For some routes, traffic volume may be so low that no surfacing is economically justified and natural soil serves as the roadway.
对于一些线路，交通量可能会很低以至于不用路面在经济上都是合理的，天然的土壤就可以直接为道路服务。
For some routes, traffic volume may be so low that no surfacing is economically justified and natural soil serves as the roadway.
对于一些线路，交通量可能会很低以至于不用路面在经济上都是合理的，天然的土壤就可以直接为道路服务。
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