That depends on what your definition of "friendly" is. But, RVs seem to be the preferred lodging at most races. Ever seen an aerial view of Bristol!? You will no doubt see more RVs at a NASCAR race than any other sporting event...that's just my opinion. I've RV'd at old Rockingham, Bristol, and Martinsville. There are RV accomodations in the general area of most tracks from a spot to park with no amenities to other areas with full hookups. Heck, at Richmond and Bristol, local residents turn their yards into campgrounds the week of the race. Mind you, camping at a race will not be very inexpensive.
Most track websites provide you with some local RV campsites. You can also search the web for campgrounds near the tracks. And then there are the campgrounds that pop up just for the race. I would say try and find someone who has RV'd at the track you want to go to and get local advise from them. Or visit the tracks during the year to research areas you can camp when the race is in town. I would also say that if you get into town on Thursday or early Friday morning before a race, you will be able to find plenty of camping spaces...maybe not what you would consider choice, but you will find a place to setup. After your first trip to a track you can figure out good campsites around the track for your next race. Send me a PM, I'll be glad to share some info on Martinsville if you are interested.
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