(S (S (BASENP (PRP It)) (VP (VP (VP (VBZ is) (RB not)) (VBN known)) (SBAR (SBAR (IN if) (S (BASENP (DT the) (NN train)) (VP (VBD went) (PP (IN through) (BASENP (DT a) (JJ red) (NN signal)))))) (CC or) (SBAR (IN if) (S (BASENP (EX there)) (VP (VBD was) (NP (BASENP (DT a) (NN problem)) (PP (IN with) (BASENP (DT the) (NN signalling)))))))))) (PERIOD .))