# Two-Area Native Road Comparison

## Runs

2026-08-14:

```bash
npm run road:compile -- --config config/areas/nantaizi-lake-innovation-valley.json
npm run build:area -- --config config/areas/hanyang-block.json --stages intermediates
npm run road:compile -- --config config/areas/hanyang-block.json
```

`comparison.json` is a coverage and diagnostic record. Feature counts are not
a geometry-quality score: osm2streets and the native compiler segment roads at
different levels.

| Area | Directional roads | Native surfaces | Native junctions | Movements | Internal ends | Manual candidates | osm2streets road surfaces |
| --- | ---: | ---: | ---: | ---: | ---: | ---: | ---: |
| nantaizi-lake-innovation-valley | 34 | 19 | 6 | 46 | 4 | 2 | 50 |
| hanyang-block | 475 | 352 | 20 | 369 | 161 | 83 | 1826 |

## Observed Failure Modes

The hanyang osm2streets/QGIS run completed, but its log reported repeated:

- roads trimmed into oblivion;
- degenerate intersections that could not be collapsed because layers, names,
  highway types, or lane specifications differ;
- intersection polygon requests with no roads.

The native compiler did not hide the related uncertainty. It reported 161
internal road ends. Eighty-three have one or more nearby, direction-compatible
candidate departures within 35 metres; these remain suggestions for explicit
review rather than automatic topology edits. The initial five one-way junctions
that lacked connector curves now publish road-surface envelopes based on their
semantic movements. Across hanyang, 369 movements are identified: 243 require
a connector curve, while 126 are continuous at their OSM node and intentionally
have no separate geometry.

## Resulting Priorities

1. Keep manual candidate suggestions and semantic overrides as the correction
   path for near-miss topology. Do not bulk-connect candidates.
2. Expand ordinary junction support from 3/4 physical approaches only after
   identifying a repeated unsupported topology; one-way movements that are
   continuous at a node are already supported without fake connector geometry.
3. Add an inspectable movement artifact so turn geometry is not the only
   representation of a road-to-road movement.
4. Use a visual review of a few explicit hanyang diagnostics before changing
   connection-distance or road-class rules.