Here are 5 Erector sets. The brand is very old, it is called "Meccano" in England, where it started out. For some reason, they changed the name to "Erector" to sell items in the USA. The sets are known for their metal parts, and sometimes motorized action. Yes! These sets are also sold in the UK area (possibly more of Europe too) but under Meccano, so you can see those on Sonic UK on Gear. The cars are probably motorized/battery items.

Everything here is a kit though, you have to build it with the mini tools they include. See the red number? (ex. 100+) that's how many parts. You can see: Sonic & Speed Star, Knuckles & LandBreaker, Sonic & Green Hill Ramp Set, Sonic Casino Street Playset, and Sonic & Knuckles race track of Chemical Plant Zone. Lots to choose from, these look fun! 

In the gallary you can see the Chemical Plant themed race set all put together. You can see it has switching areas with flipper wands to guide the cars, plus a sort of 'finish line'. At right is the "exploded view" (just means everything is hovering apart) Exploded View Car Renders
of how the racers & their cars are put together. Do note that they are renders, and not real item photos. 

Here are real photos of the figure & car you get with the set. The Erector Speed Star has raised triangle 'bolts' in the center of it, (at right) but the figure is removeable. Notice his hilarious tiny feet! This is so he fits in the car.
Nendoroid on Green Hill Track
The Jazwares 3.5 line figure (left) wasn't as "designed" to fit in his vehicle. With each set you're forced to get a vehicle, so you'll end up with several Speed Stars if you want them all. Some are motorized while others are "pull back n' go". At left is the nendoroid Sonic walking on the track, to give you an idea of the size & detail. You can see how it comes with the iconic palm trees & sun flowers. The 'goal ring' is cardboard though, so watch out!