5 stars for working lava - no doubt!
Had great fun getting my '88 Pessima "Rustoleum Racing Special" around the course a few times, and with multiple routes, it wasn't played out so quickly.
When that eventually got tiresome, I opted to bring in the reserves.... 20 pianos and a truck. I jammed about 3/4ths of the pianos in the truck and had a good time driving around the track in a T-65 box upfit, with a t1000 modded turbo (which will burn the tires off if I am not careful, but I love a giant truck that burns rubber). It was priceless trying not to roll it, or seeing the lava pits too late and hitting them and exploding.
Let's just say it's not a very 'smooth' road surface (as it's not intended to be) and thus my ears had the joyous monotony of piano muzak until I hit enough air time to tenderize said offending pianos enough to shut them up.
Eventually, the physics on my truck died an untimely death, so I resorted to running a rusty Oldsmobile into the piano heap that was left after the truck carrying them was removed. I had a good solid hour of fun at-least on what is a 'fantasy setting' loop course, almost unheard of for me as loop courses aren't normally my thing.
A few blind crests aside, I really didn't have much of an issue here. Nothing a few additional decal-style hints on the road-surface couldn't hint out if they were included in future revisions or maps (arrows, skid-marks).
And of-course, it has lava. How could this not be included in any map where it's relevant in a car-crashing/wrecking game???
Your levels keep getting better and better. You do have a bit of a problem with blind crests, though - in all three of your Motorstorm levels so far, there are a few locations where you have to turn immediately after a crest, and you don't see any signposts until it's too late. Either way, your work really brings back the atmosphere of the Motorstorm festival - keep it coming.