There were 2 different concepts for Slot Car Racing Sonic. There's been a slot track before...but it wasn't very good at all, with only stickers pasted onto ordinary cars. This one is trying to innovate. The flat-track slot-racer WAS produced, and so it's prototype photo and actual photos are now located in UK Electronics.

Neither the left nor right track is approved, and both are only drawings. The watermark on the right concept says "Unapproved". As you can see, they're going with a very similar figural-racer design to the above RC Racers. If you look closely, you can see little wheels on the heels and toes to help them race. The controllers are also Sonic & Tails themed, with colors and matching decals. The right track is more "Sonic Styled" with rings on it's surface, a tilt, and even a famous loop from Sonic 1.