( This ( ( ( is mainly ) ( ( explained ( by ( ( the growth ) ( in ( ( the volume ) ( of ( ( ( road traffic ) and ) ( an increase ) ) ) ) ) ) ) ) ( in ( ( the amount ) ( of ( ( natural gas ) ( ( used ( in ( oil ( and ( gas production ) ) ) ) ) ( in ( the ( North Sea ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (ADVP (RB mainly)) (VP (VBN explained) (PP (IN by) (NP (NP (DT the) (NN growth)) (PP (IN in) (NP (NP (DT the) (NN volume)) (PP (IN of) (NP (NP (NN road) (NN traffic)) (CC and) (NP (DT an) (NN increase)))))))) (PP (IN in) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (JJ natural) (NN gas)) (VP (VBN used) (PP (IN in) (NP (NN oil) (CC and) (NN gas) (NN production))) (PP (IN in) (NP (DT the) (NNP North) (NNP Sea)))))))))) (. .)))
This is mainly explained by the growth in the volume of road traffic and an increase in the amount of natural gas used in oil and gas production in the North Sea.
(ROOT (S (PP (IN From) (NP (NP (NNS observations)) (ADJP (RB as) (JJ simple) (PP (IN as) (S (VP (VBG blowing) (PRT (RP up)) (NP (DT a) (NN balloon)))))))) (, ,) (NP (PRP it)) (VP (VBZ is) (ADJP (JJ clear)) (SBAR (IN that) (S (S (VP (VBG increasing) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN gas)))))) (VP (VBZ increases) (NP (DT the) (NN volume)))))) (. .)))