(S (S (BASENP (DT The) (NNP UN)) (VP (VBD said) (SBAR (S (BASENP (DT the) (ADJP (NN rail) (VBN based)) (NN system)) (VP (VBZ has) (VP (VBN helped) (S (VP (TO to) (VP (VB save) (NP (NP (BASENP (NN 630,000) (NNS tonnes)) (PP (IN of) (BASENP (NN pollution)))) (BASENP (DT a) (NN year)))))))))))) (PERIOD .))