There are a few in Georgia that are commercial but mine is strictly portable. It is designed on two hollow core doors and hinges for storage and transport. The longest stretch is over 14 feet with the in field and other half being rather curvy. Full skirts and barriers and has 2 power supplies to provide max power with minimal surge. The only downside is that it is just 2 lanes but couldn't fit 4 in a fully portable layout
There is a guy in Atlanta that has 4 tracks, 1 road course, 1 oval, 1 tri oval, and the dragstrip. All are 4 lane minimum (except drag strip) and all are connected to PC for lap times. Pretty sweet setup but requires more space than I have. I'll get more info if you like.
Russ