-- Correct probe: mainline deck parts are named "Road". Barriers are found by
-- actual name, not a guess. Also verifies the ramp tip lands ON a Road part
-- (not merely near one) and that the median parapet really is open at the
-- junctions.
local ws = game:GetService("Workspace")
local map = ws:FindFirstChild("Map")
local exp = map:FindFirstChild("Expressway")

local road, runs = {}, {}
local barrierNames = {}
for _, d in ipairs(map:GetDescendants()) do
	if d:IsA("BasePart") then
		local nm = d.Name
		if nm:gsub("_?%d+$", "") == "Road" then
			table.insert(road, d)
		end
		for _, base in ipairs({ "PAEntryRampNear", "PAExitRampNear", "PAEntryRampTrunk", "PAExitRampTrunk" }) do
			if nm:sub(1, #base + 1) == base .. "_" then
				runs[base] = runs[base] or {}
				table.insert(runs[base], d)
			end
		end
		if
			nm:lower():find("barrier")
			or nm:lower():find("parapet")
			or nm:lower():find("wall")
			or nm:lower():find("rail")
		then
			local b = nm:gsub("_?%d+$", "")
			barrierNames[b] = (barrierNames[b] or 0) + 1
		end
	end
end

local out = {}
table.insert(out, "roadDeckParts=" .. #road)
local bn = {}
for k, v in pairs(barrierNames) do
	table.insert(bn, k .. "=" .. v)
end
table.sort(bn)
table.insert(out, "barrier-ish: " .. table.concat(bn, " "))

local function sortKey(p)
	return tonumber(p.Name:match("_(%d+)$")) or 0
end

-- Ramp tip -> nearest Road part, horizontal and vertical separately.
for _, base in ipairs({ "PAEntryRampNear", "PAExitRampNear" }) do
	local parts = runs[base]
	if not parts then
		table.insert(out, base .. ": MISSING")
		continue
	end
	table.sort(parts, function(a, b)
		return sortKey(a) < sortKey(b)
	end)
	for _, which in ipairs({ { "head", parts[1] }, { "tail", parts[#parts] } }) do
		local p = which[2]
		local bestH, bestDY = math.huge, 0
		for _, m in ipairs(road) do
			local h = (Vector3.new(p.Position.X, 0, p.Position.Z) - Vector3.new(m.Position.X, 0, m.Position.Z)).Magnitude
			if h < bestH then
				bestH = h
				bestDY = p.Position.Y - m.Position.Y
			end
		end
		table.insert(out, ("%s %s: horizToRoad=%.1f dY=%.1f"):format(base, which[1], bestH, bestDY))
	end
end
return table.concat(out, "\n")