Research Article
Theoretical Research on Longitudinal Profile Design of Superhighways
Table 3
Comparison of the different superhighway grades.
| Grade | Vehicle type | Construction mode | Expected construction time |
| Grade I | Cars and trucks | Retrofitting existing highways | 15 years | Grade II | Only for cars | According to passenger-dedicated railway specifications | 30 years | Grade III | Only for autonomous vehicles | According to high-speed railways | 40–50 years |
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