Likely a pre-configured modpack . The community frequently creates these to fix the game's notorious bugs or to add hundreds of real-world cars and engines.
Usually, these are "stand-alone," meaning you just extract the folder and run the SLRR.exe . street-legal-racing-redline-build-9951964-rar
Reduced "Desktop Crashes" (though some are inevitable in this engine). ⚠️ Installation & Safety Likely a pre-configured modpack