Complex sentence: The trains were put into service from July 1 2002 after a small amount of testing and replaced ageing 1960s Tulloch trailers, all of which were withdrawn by 31 March 2004.
Split into simpler sentences: The trains were put into service from July 1,2002 after a small amount of testing. The arrival of the Millennium trains triggers retirement of the aging 1960s Tulloch trailers, they were all withdrawn by 31 March 2004.