Complex sentence: In 2003, the company managed and maintained 25% of English and until 2007 50% of Scottish trunk roads, now less than 25% and held a 12% share of the rail maintenance market.
Split into simpler sentences: In 2003, the company managed and maintained 25% of English and, until 2007,50% of Scottish trunk roads; it now manages less than 25%. It also held a 12% share of the rail maintenance market.