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).

mod/content/overtake_probe.script.tl

@@ -26,6 +26,13 @@ local function turnaround(edge : EdgeId) : integer
 	return tn.turnaroundEdges[edge.index + 1]
 end
 
+-- short street template name of a segment, so passing-lane use on the prototype road can be told apart
+local function roadOf(seg : integer) : string
+	local be = api.engine.getComponent(seg, api.type.ComponentType.BASE_EDGE) as Engine.Component.BaseEdge
+	if be == nil then return "?" end
+	return (tostring(be.roadTemplate):match("([^/]+)%.street_template$")) or tostring(be.roadTemplate)
+end
+
 local function dump(dt : number)
 	local player = api.engine.util.getPlayer()
 	local vehicles = api.engine.getEntitiesWithComponent(api.type.ComponentType.TRANSPORT_VEHICLE, { requireOwnedByPlayer = player })
@@ -37,8 +44,8 @@ local function dump(dt : number)
 		if lv ~= nil and not lv.isTram and mp ~= nil then
 			local edge, dir = edgeAt(mp)
 			p(string.format(
-				"veh=%d seg=%d lane=%s dir=%s turnaround=%s edgeIndex=%d/%d pos=%.1f speed=%.2f state=%s tvState=%s line=%s standing=%.1f",
-				v, edge and edge.entity or -1, tostring(edge and edge.index), tostring(dir), tostring(edge and turnaround(edge)),
+				"veh=%d road=%s seg=%d lane=%s dir=%s turnaround=%s edgeIndex=%d/%d pos=%.1f speed=%.2f state=%s tvState=%s line=%s standing=%.1f",
+				v, edge and roadOf(edge.entity) or "-", edge and edge.entity or -1, tostring(edge and edge.index), tostring(dir), tostring(edge and turnaround(edge)),
 				mp.dyn.pathPos.edgeIndex, #(mp.path.edges as {any}), mp.dyn.pathPos.pos, mp.dyn.speed, tostring(mp.state),
 				tostring(tv and tv.state), tostring(tv and tv.line), mp.dyn.timeStanding))
 		end

mod/content/streets/overtake_proto_a.street_template.lua

@@ -20,10 +20,10 @@ return {
 		laneConfigs = {
 			{ forward = false, height = 0, offset = -1,   speed = 22.22, transportModes = { "PERSON", "CARGO" }, width = 2 },
 			{ forward = false, height = 0, offset = -0.5, speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 5 },
-			-- backward passing lane, meant to sit over the forward driving lane
-			{ forward = false, height = 0, offset = 2.5, speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 0.5 },
-			-- forward passing lane, meant to sit over the backward (oncoming) driving lane
-			{ forward = true,  height = 0, offset = -2.5, speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 0.5 },
+			-- backward passing lane, meant to sit over the forward driving lane (BUS/TRUCK only: keeps town cars out)
+			{ forward = false, height = 0, offset = 2.5, speed = 22.22, transportModes = { "BUS", "TRUCK" }, width = 0.5 },
+			-- forward passing lane, meant to sit over the backward (oncoming) driving lane (BUS/TRUCK only)
+			{ forward = true,  height = 0, offset = -2.5, speed = 22.22, transportModes = { "BUS", "TRUCK" }, width = 0.5 },
 			{ forward = true,  height = 0, offset = 0.5,  speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 5 },
 			{ forward = true,  height = 0, offset = 1,    speed = 22.22, transportModes = { "PERSON", "CARGO" }, width = 2 },
 		},

mod/content/streets/overtake_proto_b.street_template.lua

@@ -20,10 +20,10 @@ return {
 		laneConfigs = {
 			{ forward = false, height = 0, offset = -1,   speed = 22.22, transportModes = { "PERSON", "CARGO" }, width = 2 },
 			{ forward = false, height = 0, offset = -0.5, speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 5 },
-			-- backward passing lane, meant to sit over the forward driving lane
-			{ forward = false, height = 0, offset = -2.5, speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 0.5 },
-			-- forward passing lane, meant to sit over the backward (oncoming) driving lane
-			{ forward = true,  height = 0, offset = 2.5, speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 0.5 },
+			-- backward passing lane, meant to sit over the forward driving lane (BUS/TRUCK only: keeps town cars out)
+			{ forward = false, height = 0, offset = -2.5, speed = 22.22, transportModes = { "BUS", "TRUCK" }, width = 0.5 },
+			-- forward passing lane, meant to sit over the backward (oncoming) driving lane (BUS/TRUCK only)
+			{ forward = true,  height = 0, offset = 2.5, speed = 22.22, transportModes = { "BUS", "TRUCK" }, width = 0.5 },
 			{ forward = true,  height = 0, offset = 0.5,  speed = 22.22, transportModes = { "CAR", "BUS", "TRUCK" }, width = 5 },
 			{ forward = true,  height = 0, offset = 1,    speed = 22.22, transportModes = { "PERSON", "CARGO" }, width = 2 },
 		},