Road design basics
Road design is not simply drawing a line. It balances terrain, speed, road function, construction constraints, and safety checks into a geometry that can actually be driven.
Image source: Basic functional road classes.svg, published as CC0 / public domain by the author, used here as a functional road hierarchy reference.
| Layer | Design question | Typical in-game validation |
|---|---|---|
| Corridor | What areas does the road serve and avoid? | Route crosses restricted terrain |
| Horizontal alignment | How do tangents, circular curves, and transitions connect? | Radius too small, curvature jump |
| Vertical profile | Are grades and vertical curves continuous and drivable? | Grade too steep, crest visibility issue |
| Cross section | How are lanes, shoulders, slopes, and drainage arranged? | Slope too steep, roadbed width issue |
| Safety check | Can a vehicle pass and stop safely? | Sight distance, superelevation, or stability warning |