Research Article
Green Supply Chain Network Design with Economies of Scale and Environmental Concerns
Table 1
Unit transport cost and CO2 emissions.
| ā | Highway | Railway | Air transportation |
| Unit transport cost ($/t-km) | 0.42 | 0.35 | 0.50 | Unit CO2 emissions (kg/t-km) | 0.14 | 0.08 | 0.06 |
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