investigations of the braking failures that would require the entire fleet of trains to be withdrawn from service. Testing of affected trains was carried out on the Werribee line between Newport and Laverton, with soapy water sprayed onto the rails to increase the amount of wheel slip experienced, in an effort to replicate the brake fault. The entire fleet has now re-entered service, although with a restriction not to run single unit (3 car) operations. In December 2008 train operator Connex commenced proceedings in the Supreme Court to claim damages from Siemens. Connex claims Siemens provided trains with a braking system that was "defective, faulty and inadequate", the trains being "not fit for their purpose" and were not of "merchantable quality". In March 2009, it was reported that three Siemens Nexas trains had been impounded due to new braking incidents in the week prior. By December 2010 sanding equipment was trialled on set 773M-2537T-774M in order to improve braking performance of the trains, and by February 2011 a number of in-service trains had also been fitted with the equipment. The sand boxes are fitted to the middle two bogies of each 3-car set. In June 2011 installation of sanding equipment was completed across the entire fleet. Speed restrictions have now been lifted on all Siemens Nexas trains. In September 2011 the Office of the Chief Investigator for transport safety found that "the relatively high frequency of overruns involving Nexas trains was neither the result of individual train defects nor any deficiency in train maintenance". Design & construction The bodies of the Siemens Modular Metro trains evolved from the 1993 DT2 Series used in the Nuremberg U-Bahn whose design in turn came from production of the A Series built for the nearby Munich U-Bahn. The version of Siemens metro train designed for Melbourne included several attributes similar to existing Melbourne suburban electric trains such as being single-deck and operating in M-T-M (motor-trailer-motor) sets of three carriages, where the motor cars each have an overhead pantograph, and two of these 3-car sets are generally coupled together to form a 6-carriage train when run in revenue service, though a single set may be run when demand does not merit a full train. All were built by Siemens Transportation Systems, Vienna with the final fitout completed at Newport Workshops. There are several notable differences between the Siemens Nexas trains and other trains which operate