Tokyu 5000 series (2002)/Tokyu 5050-4000 series

The Tokyu 5050-4000 series, also known as the 4000 series, is a Japanese city commuter electric multiple unit operated by the Tokyu Corporation since September 2011 on the Tokyu Tōyoko Line.
==History==
The 5050-4000 series sets are a ten-car derivative of the 5050 series sets intended for through operation to the Tokyo Metro Fukutoshin Line. A total of 102 cars were manufactured from 2011 to 2019, with two cars initially serving as spare cars intended for emergency use. One set, 4110, features a unique black and gold livery to promote the Shibuya Hikarie building.
5050 series set 5173 was reformed into set 4111 by inserting the two spare cars into the set.
In July 2022, another former 8-car set 5166 was reformed into 10-car set 4112 with two new “Q-Seat” cars in preparation for reserved seating service on the Toyoko Line in 2023. As of 1 August 2022, the new Q-Seat cars feature a livery very similar to those used on the Oimachi Line, however they are painted in red in contrast to orange. Two months later, three more sets (5167, 5168, and 5169) were announced to be lengthened into 10-car trainsets in preparation for through-running service on the Sotetsu Line. Once completed, they will be renumbered to sets 4113, 4114, and 4115 respectively. The first "Q-Seat" cars entered service on the Toyoko Line on 24 October 2022; however full commencement of "Q-Seat" services will begin in February 2023.
==Design==
The 5050-4000 series cars use a contemporary design featuring a flat front and top-mounted recessed headlights; these have since been replaced with LED fixtures. As they are mainly used on the Tōyoko line the cars have a pink band running down the sides of the cars. Set 4110 features a unique black and gold livery to promote the Shibuya Hikarie building; one stanchion in the train features a heart symbol as a whimsical way to improve commuters's moods.
==Specifications==
Construction of the cars is of stainless steel. The sets are based on the JR East E231 series cars and share some mechanicals. The sets use Hitachi IGBT variable frequency drive traction systems which produce a sharp hissing noise.
Category:Electric trainsets
Category:Tokyu trains
Category:J-TREC locomotives
Category:Tokyu Car locomotives