12 Volt is an arcade racing game that was in development by Sproing in 2003 / 2004 for the Playstation 2, Xbox and GameCube. The game was set in slot-car tracks and players would have been able to race their models in houses and gardens. 12 Volt looked like a mix between Re-Volt and another cancelled Nintendo 64 game, Mini Racers: it’s unknown why Sproing never released this project or how much it was completed before being canned.
Some more info can be read in the original press release:
The cars can move freely on the track, they are not bound to a specific lane or slot like conventional slot cars are! This way the game combines the look of a die-cast-racer with the feeling of a full-physics arcade rally game!
Highly realistic physics enable the player to activate toys and tools that work as weapons against other players. Imagine plunging through a heap full of marbles crashing at you in a world that really looks and feels like a childhood dream-come-true. Special magnetic rails even allow you to hook on to the inner side of hairpins and drive through them at full speed!
A GBA version was planned (and cancelled) too, but they did not even show any screens from this portable version.
Thanks to Userdante for the contribution!