I just found out that the Louisiana version is taking place in a couple of weeks, and will probably do this. It consists of 20k, 10k and 5k TTs, in that order.

There's no mention of this on the USAC page for LA. It seems that these are in a hermetically sealed container, set away from other racing activity. I didn't recognize any of the names of the past winners, either. Is this the same in other places?