This article introduces ATAB, a tool that automatically generates pairwise reachability checks for action trees. Action trees can be used to study the behaviour of real-world concurrent programs. ATAB encodes pairwise reachability checks into alternating tree automata (ATA) that determine whether an action tree has a schedule where any pair of given points in the program are simultaneously reachable. Because the pairwise reachability problem is undecidable in general ATAB operates under a restricted form of lock-based concurrency. ATAB produces ATA that are more compact and more efficiently checkable than those that have been previously used. The process is entirely automated, which simplifies the process of encoding checks for more complex action trees. The ATA produced are easier to scale to large numbers of locks than previous constructions.