Original sentence: However, this did not delay the introduction of Desiro rolling stock built by Siemens to replace the old slam-door trains which are coming to the end of their useful lives.In addition, the Desiros have many more components: all are computerised and subject to more breakdowns.It is estimated the the slam-door trains could achieve 60 000 miles (96 000km) withour breakdown; the Desiros an estimated 13 000 miles (20,800km) for that reason (see this article).Some will be retained in heritage railways and on the Lymington Flyer.The final slam door train on regular passenger services ran from Waterloo on 26 May 2005.The introduction was delayed because of the additional power needs of this type of stock: Network Rail spent £1 million upgrading the power supply to take account of this.The new trains, although providing faster acceleration, need more time at station stops, since there are fewer doors, all dependent on the train coming to a standstill before they can be opened (although there were safetyhazards with the previous stock in that respect)
Edited sentence: However, this did not delay the long-awaited introduction of new Desiro rolling stock built by Siemens to replace the old slam-door trains which are coming to the end of their useful lives.The old slam-door stock is expected to be replaced by mid-2005