I think what might be confusing is that NRHA has changed what they call their classes. They went from Open Int Open Limited Open and Rookie Pro to L1 L2 L3 and L4. They are still devided up according to earnings and yes some will run at the same time. Normally the L3 and L4 will run at the same time L2 and L1 will run on their own. Yet as some shows they will all run to gether. Just depends on who things are being done by the show commitie.