function Road::_Cost(self, path, new_tile, new_direction)
{
	/* path == null means this is the first node of a path, so the cost is 0. */
	if (path == null) return 0;

	local prev_tile = path.GetTile();

	/* If the new tile is a bridge / tunnel tile, check whether we came from the other
	 * end of the bridge / tunnel or if we just entered the bridge / tunnel. */
	if (AIBridge.IsBridgeTile(new_tile)) {
		if (AIBridge.GetOtherBridgeEnd(new_tile) != prev_tile) {

			/* Check for a turn. We do this by substracting the TileID of the current node from
			 * the TileID of the previous node and comparing that to the difference between the
			 * previous node and the node before that. */
			local cost = self._cost_tile;
			if (path.GetParent() != null && (prev_tile - path.GetParent().GetTile()) != (new_tile - prev_tile) &&
					AIMap.DistanceManhattan(path.GetParent().GetTile(), prev_tile) == 1) {
				cost += self._cost_turn;
			}

			/* Check if the last tile was sloped. */
			if (path.GetParent() != null && !AIBridge.IsBridgeTile(prev_tile) && !AITunnel.IsTunnelTile(prev_tile) &&
					AIMap.DistanceManhattan(path.GetParent().GetTile(), prev_tile) == 1 && self._IsSlopedRoad(path.GetParent().GetTile(), prev_tile, new_tile)) {
				cost += self._cost_slope;
			}

			if (!AIRoad.AreRoadTilesConnected(prev_tile, new_tile)) {
				cost += self._cost_no_existing_road;
			}

			return path.GetCost() + cost;
		}
		return path.GetCost() + (AIMap.DistanceManhattan(new_tile, prev_tile) + 1) * (self._cost_tile + self._cost_bridge_per_tile) - self._cost_tile + self._GetBridgeNumSlopes(new_tile, prev_tile) * self._cost_slope;
	}
	if (AITunnel.IsTunnelTile(new_tile)) {
		if (AITunnel.GetOtherTunnelEnd(new_tile) != prev_tile) {

			/* Check for a turn. We do this by substracting the TileID of the current node from
			 * the TileID of the previous node and comparing that to the difference between the
			 * previous node and the node before that. */
			local cost = self._cost_tile;
			if (path.GetParent() != null && (prev_tile - path.GetParent().GetTile()) != (new_tile - prev_tile) &&
					AIMap.DistanceManhattan(path.GetParent().GetTile(), prev_tile) == 1) {
				cost += self._cost_turn;
			}

			/* Check if the last tile was sloped. */
			if (path.GetParent() != null && !AIBridge.IsBridgeTile(prev_tile) && !AITunnel.IsTunnelTile(prev_tile) &&
					AIMap.DistanceManhattan(path.GetParent().GetTile(), prev_tile) == 1 && self._IsSlopedRoad(path.GetParent().GetTile(), prev_tile, new_tile)) {
				cost += self._cost_slope;
			}

			if (!AIRoad.AreRoadTilesConnected(prev_tile, new_tile)) {
				cost += self._cost_no_existing_road;
			}

			return path.GetCost() + cost;
		}
		return path.GetCost() + (AIMap.DistanceManhattan(new_tile, prev_tile) + 1) * (self._cost_tile + self._cost_tunnel_per_tile) - self._cost_tile;
	}

	/* If the two tiles are more than 1 tile apart, the pathfinder wants a bridge or tunnel
	 * to be built. It isn't an existing bridge / tunnel, as that case is already handled. */
	if (AIMap.DistanceManhattan(new_tile, prev_tile) > 1) {
		/* Check if we should build a bridge or a tunnel. */
		if (AITunnel.GetOtherTunnelEnd(new_tile) == prev_tile) {
			return path.GetCost() + (AIMap.DistanceManhattan(new_tile, prev_tile) + 1) * (self._cost_tile + self._cost_tunnel_per_tile + self._cost_no_existing_road) - self._cost_tile;
		} else {
			local cost = (AIMap.DistanceManhattan(new_tile, prev_tile) + 1) * (self._cost_tile + self._cost_bridge_per_tile + self._cost_no_existing_road) - self._cost_tile + self._GetBridgeNumSlopes(new_tile, prev_tile) * self._cost_slope;
			/* Check if the new tile is a coast tile. */
			if (AITile.IsCoastTile(new_tile) && AITile.HasTransportType(new_tile, AITile.TRANSPORT_WATER)) {
				cost += self._cost_coast;
			}
			return path.GetCost() + cost;
		}
	}

	/* Check for a turn. We do this by substracting the TileID of the current node from
	 * the TileID of the previous node and comparing that to the difference between the
	 * previous node and the node before that. */
	local cost = self._cost_tile;
	if (path.GetParent() != null && (prev_tile - path.GetParent().GetTile()) != (new_tile - prev_tile) &&
			AIMap.DistanceManhattan(path.GetParent().GetTile(), prev_tile) == 1) {
		cost += self._cost_turn;
	}

	/* Check if the new tile is a coast tile. */
	if (AITile.IsCoastTile(new_tile) && AITile.HasTransportType(new_tile, AITile.TRANSPORT_WATER)) {
		cost += self._cost_coast;
	}

	/* Check if the last tile was sloped. */
	if (path.GetParent() != null && !AIBridge.IsBridgeTile(prev_tile) && !AITunnel.IsTunnelTile(prev_tile) &&
			AIMap.DistanceManhattan(path.GetParent().GetTile(), prev_tile) == 1 && self._IsSlopedRoad(path.GetParent().GetTile(), prev_tile, new_tile)) {
		cost += self._cost_slope;
	}

	if (!AIRoad.AreRoadTilesConnected(prev_tile, new_tile)) {
		cost += self._cost_no_existing_road;
	}

	return path.GetCost() + cost;
}