Outsourcing group Serco said customers' need to improve efficiency in the current economic climate is providing it with more opportunities to win contracts as it reported continued strong trading.Serco, whose activities include operating London's Docklands Light Railway and vans used to transport prisoners, said it remains on track to deliver on its financial guidance for 2009.It said that it has been awarded £1bn worth of contracts in the second half, bringing the total for the year so far to £4.5bn. In the US it has won contracts with a total value of about $700m.'In the current global economic climate, our customers continue to face significant challenges in increasing the efficiency of essential services,' it said.'These are driving further potential opportunities for us in both existing and new markets.'