website. Both were repainted in 2017 into the same black and yellow livery carried by the refurbished Metrocars, but in September 2019, Metrocar 4001 underwent further repainting into a 40 Years livery with all four previous liveries amalgamated into one. In August 2019, Metrocar 4040 was repainted into the black and yellow livery, and 4083 followed shortly after in May 2020. As a consequence of this, the only liveries that currently exist are the standard black and yellow, and the 40 Years celebration livery on 4001. Electrics The network is electrified with a overhead line system. This voltage was previously used on and number of United Kingdom lines, including the Woodhead line, but is now unique. Each Metrocar has its own Brecknell Willis pantograph for collecting power from the overhead line. The sections of Metro owned by Nexus have a maximum speed of in some areas, which matches the top speed of the rolling stock. The vehicles have a minimum curve radius of , although there are no curves this tight except for the non-passenger chord between Manors and West Jesmond. Formation During the early years of Metro, units were operated in single and double sets. As single units became overcrowded, Nexus resumed using two units as standard. Single units again became common during construction of the Sunderland extension when some units were taken for testing of the new track. During original construction, the Metro system was designed to use three unit sets, and some platforms were constructed to accommodate this; however, due to a lack of funding, this was not possible. As a result, the units run in sets of two. Announcements The "stand clear of the doors please" announcement, which sounded before the doors started to close, was introduced in 1991. In order to increase the clarity of the announcement (especially for individuals not fluent in English) the phrase was replaced with "doors closing" in 2004. In 2011, the "doors closing" recording was replaced in post-refurbishment Metrocars with a simple beeping sound, similar to that of the London Underground. The train emits a solid 3-second beep when the doors are released, and a rapid 3-second beeping immediately before the doors are closed, in line with the 2010 UK Rail Vehicle Accessibility Regulations (RVAR). When the automated next station announcements were introduced they featured a female announcer, however during late 2014 this was replaced with a male announcer. The