The README describes the track plans as they are drawn

It promised higher ground shown brighter, which the flat masks never
did, and it predated the change that draws each wall bar as one line
rather than a box.

pack-dist.ps1

@@ -303,8 +303,10 @@ does different jobs depending on which preset is lit.
 
 TRACKS.html is every track seen from above. The game has no track maps
 in it - the console had pictures and they did not survive - so each plan
-is drawn from the track's own scenery, placed where the game places it,
-with higher ground shown brighter.
+is drawn from the track's own scenery, placed where the game places it.
+Nearly every track is one wall bar repeated a few hundred times, and at
+this size a bar reads as a line rather than a box, so each is drawn as
+the single line it reads as.
 
 Four files here are yours. None of them ship - the game writes each one
 the first time it needs it and then leaves it alone, so a new build