Horizontal curve
Horizontal curves define how vehicles turn on the map. A practical alignment usually combines tangents, circular curves, and transition curves to balance terrain avoidance, comfort, and stability.
Image source: Cal Highway 17 curves.jpg by Minesweeper, CC BY-SA 3.0 / GFDL, used here as a reference for successive horizontal curves.
| Design speed | Illustrative minimum radius | Editor note |
|---|---|---|
| 40 km/h | about 60 m | Low-speed or site roads |
| 60 km/h | about 150 m | Check superelevation and sight distance |
| 80 km/h | about 280 m | Use transitions and run a driving validation |