There doesn't always have to be a block brake mid course to run 3 trains on a coaster
Wicker Man at Alton Towers is a good example, the lift acts as the block on that ride as could the quadruple launch section on this ride. It could E stop on the 4th launch if the previous train hasn't cleared the final brake run.
So you could have one train finishing up the ride circuit, one loading and one beginning the quadruple launch sequence.