"Don't be absurd," you say. "Twenty thousand cars wouldn't fit on the start line". You're right—they don't, and the result of layering replay upon replay is a mesmerising flow of steel and rubber that took 300 hours to render. Distinct cars blossom from the chromium mass, crashing back down before fountaining over jumps or toppling backwards into the sea.
Each one of the cars in this video was, at one point, driven by a real human who submitted their Trackmania United and Trackmania Forever records to YouTuber L4Bomb4 to be compiled into one almighty race in the newer Maniaplanet version of Trackmania Stadium (unique skins were lost in the process).
However, 'only' 12,000 of the cars could be rendered simultaneously "at a pretty high quality"—anything more and the game crashed. Not one to be deterred by such obvious development oversights, editor Danixks made a custom chroma key mod to blend the remaining 8,000 replays into the finished video. Madness.
Apart from being pretty, the video doubles as a visualisation of the big data that developers work with when building levels, highlighting crash hotspots, bottlenecks and the idiots like me who ram the first pillar.