Documentation: Fix explanation of road stops terrain type variable

docs/newgrf-roadstops.html

@@ -243,8 +243,16 @@
 	The remaining bits are reserved for future use and should be masked.
 	</p>
 
-	<h4 id="roadstop_terrain_type">Road stop tile/terrain type (42, or mappable variable: roadstop_terrain_type)</h4>
-	<p>This has the same value as <a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Objects#Tile_information_.2841.29">object (feature F) variable 41</a>.</p>
+	<h4 id="roadstop_terrain_type">Road stop tile terrain type (42, or mappable variable: roadstop_terrain_type)</h4>
+	<p>This has the same value as bits 0 - 7 of <a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Objects#Tile_information_.2841.29">object (feature F) variable 41</a>.
+		<table>
+		<tr><th>Value</th><th>Meaning</th></tr>
+		<tr><td>0</td><td>Normal</td></tr>
+		<tr><td>1</td><td>Desert</td></tr>
+		<tr><td>2</td><td>Rainforest</td></tr>
+		<tr><td>4</td><td>On or above snowline</td></tr>
+		</table>
+	</p>
 
 	<h4 id="roadstop_road_type">Road stop road type (43, or mappable variable: roadstop_road_type)</h4>
 	<p>This has the value of the (translated) roadtype the road stop is built on, or the current roadtype in the build GUI. If the roadtype has no entry in the roadtype translation table of the GRF, this value will be 0xFF. If no translation table is present, the raw value will be returned. Note: only exact matches of roadtypes are reported. If the translation table of the GRF does not contain the exact roadtype 0xFF is returned.<br />