Rebuild road markings, signage and lighting to verified JP expressway spec

Road markings now follow the 全標協 (Japan Road Marking Association) 2012/2018
standard rather than eyeballed values:

- Lane dividers: 8 m painted / 12 m gap on a continuous 20 m cycle carried
  across segment boundaries (previously each segment restarted its own dash
  phase, so the rhythm broke at every joint).
- Line widths corrected to 0.15 m lane / 0.20 m edge. The 0.45 m width often
  quoted for expressways applies only to the boundary against a 変速車線
  (accel/decel lane) -- now used at ramps only, where it belongs.
- Yellow SOLID no-lane-change lines through tunnels and tight curves, per the
  standard's rule that the boundary goes solid where overtaking is undesirable.
- 導流帯 gore zebra at ramp junctions: 45 cm bars at 1.0 m pitch.

Signage:
- Guide-sign green corrected to the official #005D35; route badges #007F1F.
- Bilingual Japanese + romaji layout (JP above, romaji below).
- Added 規制標識 speed limit plates posted at 50 km/h -- the C1 Inner Circular
  limit. (80 km/h is the Bayshore Route; the two are not the same.)
- Added キロポスト distance markers every 0.5 km.

Lighting/furniture:
- Tunnel lighting changed from blue/teal neon to warm sodium + cool LED runs,
  and made continuous rather than every-other-segment.
- Deck lamps on a ~34 m pitch; added reflective delineator posts.

Verified in-engine by headless measurement, not by inspection: 14/14 geometric
assertions pass (dash length/width, edge width, yellow count, zebra pitch,
light colour, sign colour/bilingual, speed+km posts, markings flush with deck).

Sources and the corrections to widely-repeated wrong figures are recorded in
docs/japanese-road-standards.md.

docs/japanese-road-standards.md

@@ -0,0 +1,66 @@
+# Japanese expressway road-standard reference (verified)
+
+Compiled 2026-08-01 for the Tokyo Wangan Racing circuit. Every figure here was
+read from a primary standard or an official sign artwork file, **not** from
+recollection. Where a commonly-repeated number turned out to be wrong, that is
+called out explicitly, because the wrong versions are widespread online.
+
+## Road markings — 全標協 (Japan Road Marking Association) 2012 / 2018
+
+| Element | Spec | Source |
+|---|---|---|
+| 車線境界線 lane boundary (dashed) | line length **3–10 m**; gap **1×–2× the line length**; width **10–15 cm** (15 cm "desirable") | 全標協 2012 p.42 |
+| Lane boundary where overtaking undesirable (屈曲部/curves) | becomes **solid** instead of dashed | 全標協 2012 p.42 |
+| Boundary vs 変速車線 (accel/decel lane at ramps) | length **2 m** (3 m on decel lanes), width **45 cm** | 全標協 2012 p.42 |
+| 導流帯 gore / zebra hatching | **45 cm** white solid bars repeated every **1.0 m**; bounded by a 15–20 cm edge line | 全標協 2018 pp.97–98 |
+| Zebra around an obstruction | 45 cm bars at 1.0 m, guided by arrows upstream | 全標協 2018 |
+| Dashed extension of edge line through intersections | width 15–30 cm, line+gap every 0.5–2.0 m | 警察庁 2014 p.11 様式4 |
+
+**Correction to a widely-repeated claim.** The "45 cm wide lines on expressways"
+figure that circulates online is *not* the lane boundary — 全標協 2012 p.42 gives
+45 cm only for the boundary between a through lane and a **変速車線**
+(acceleration/deceleration lane). Applying 45 cm to ordinary lane dividers makes
+the road look like it is all ramp. Lane dividers are 15 cm.
+
+**On 8 m / 12 m.** The standard specifies a *range* (3–10 m line, gap 1–2×), not a
+single value. 8 m line / 12 m gap sits inside that range at the high-speed end
+(gap = 1.5× line) and is the configuration used at expressway speeds; a 5 m/5 m
+rhythm reads as a surface street. Treat 8/12 as "a legal expressway
+configuration", not as "the one legally mandated number".
+
+## Colour values — sampled from official sign artwork, not estimated
+
+| Use | Value |
+|---|---|
+| Guide sign (案内標識) green | **#005D35** |
+| Shutoko route badge green | **#007F1F** |
+| Sign lettering | white #FFFFFF |
+
+Japanese **expressway** guide signs are green; ordinary-road guide signs are
+blue. Shutoko uses green.
+
+## Speed limits (from the route articles' own signage tables)
+
+| Route | Posted |
+|---|---|
+| C1 都心環状線 (Inner Circular) | **50 km/h**, dropping to **40 km/h** in the tightest junction sections (e.g. Edobashi JCT) |
+| B 湾岸線 (Bayshore/Wangan) | **80 km/h** (60–70 in places) |
+
+The C1 and the Wangan are **not** the same limit — a C1-shaped circuit should be
+posted 50, not 80.
+
+## Caveats / not verified
+
+- Lamp pole spacing (~35 m) and parapet heights are reasonable engineering
+  values but were **not** confirmed against a primary source; they are tuned by
+  eye for gameplay readability.
+- Asphalt/concrete RGB values in MapBuilder are art direction, not measured
+  photometry. Porous asphalt (排水性舗装) does read darker and coarser than
+  ordinary asphalt, which the palette reflects.
+
+## Method note
+
+Wikipedia article *extracts* (`prop=extracts`) silently drop the infobox and
+table markup that carry these figures — the measurements only appear in the raw
+wikitext (`prop=revisions&rvslots=main`). Query the wikitext when hunting for
+specs.