chore(prototype): passing lanes BUS/TRUCK only; probe logs road template

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/research/vehicle-probe.md

@@ -91,3 +91,10 @@ The human confirmed in game what the log showed: rebuilding the segment under a
 - So the error is not about callbacks or threads: **the exchange refuses a `MovePath`**, consistent with its doc comment (`EmissionEmitter` or `ModelInstanceList` only).
 - **Conclusion: no script API can write a road vehicle's position or route.** Moving a vehicle past another (jump, flip, teleport) is impossible for line vehicles. The only exception is `jumpToDepotEntity`, which can only target a depot.
 - The probe retried every frame (5951 errors) because the error came before the counter was incremented. The experiment is removed, and the probe is logging-only again.
+
+## Overlaid passing lanes (ticket "Can a street type with overlaid passing lanes fake overtaking on single-lane roads?")
+
+- Prototype: `mod/content/streets/overtake_proto_{a,b}.street_template.lua`, copies of `country_new_small` with a 0.5 m passing lane per direction at the centre line, offset ±2.5 into the oncoming lane (A and B use opposite signs). A mod street template sits anywhere under `content/` and refers to base resources with `::/…`.
+- First in-game run (human, 2026-10-05): the template loads, the lanes are visibly offset as intended, and vehicles can drive on the passing lanes. **Town (non-player) cars sometimes choose the passing lane.** **A faster bus behind a slower vehicle does not switch to the empty lane**: the switching logic is missing.
+- Changes for the next run: passing lanes allow only `BUS`/`TRUCK` (keeps private `CAR` town traffic out), and the probe logs the road template per vehicle (`road=`), since lane indices 2/3 also mean ordinary lanes on `country_new_medium`.
+- Hypothesis for the switch: the engine only re-chooses lanes at segment boundaries (`GetNextEdgeTrafficPenaltyAndAlternatives`), so short segments give a blocked bus more chances to pick the passing lane. Fallback trigger: `replaceSegment` ahead of the pair (made the leader re-plan lanes on multilane roads).