(S (S (S (BASENP (DT The) (NN bus)) (VP (VBD left) (BASENP (DT the) (NN road)))) (SBAR (WHADVP (WRB when)) (S (BASENP (PRP it)) (VP (VP (VP (VP (VBD skidded) (PRT (RP off))) (BASENP (DT a) (JJ tight) (NN bend))) (CC and) (VP (VBD struck) (BASENP (DT a) (NN concrete) (NN barrier))) (COMMA ,)) (S (VP (VP (VBG rolling) (PRT (RP over))) (CC and) (VP (VBG catching) (BASENP (NN fire))))))))) (PERIOD .))