The was a Japanese Shinkansen high-speed train type operated by the East Japan Railway Company (JR East) between 1992 and 2010 on Tsubasa services on Japan's first mini-Shinkansen line, the Yamagata Shinkansen branch from the main Tōhoku Shinkansen.
The fleet of 400 series trains was leased by JR East from the owning company, , a third-sector company jointly owned by JR East and Yamagata Prefecture.
The trains were originally formed as six-car sets, but a seventh car was added to each set in 1995 due to the popularity of the Tsubasa services.
Pre-series set
The pre-series set, S4, was delivered in October 1990 and unveiled to the press on 26 October 1990. It was a six-car set, arranged as shown below, with all cars motored.
{| class="wikitable"
! Car No.
! style="background: #E6FFE6"| 1
! 2
! 3
! 4
! 5
! 6
|-
! Numbering
| style="background: #F5FFF5"| 401-1
| 402-1
| 403-1
| 404-1
| 405-1
| 406-1
|-
! Seating capacity
| style="background: #F5FFF5"| 20
| 67
| 60
| 68
| 64
| 56
|}
The unit featured three different types of bolsterless bogies: DT9028 on cars 1 and 3, DT9029 on cars 2 and 4, and DT9030 on cars 5 and 6. The Green car seats were fitted with seat-back television screens, a feature not adopted on subsequent production sets.
Test running continued into 1992, with set S4 reaching Tokyo for the first time on 20 May 1992. The pre-series set was subsequently modified to production-standard specifications, becoming set L1 on 29 June 1992. However, one set, L3, remained in service until 18 April 2010, with the date chosen to mark 18 years of service. This final 400 series Shinkansen was coupled to an E4 series train during its last run.
Preservation
The first eleven sets to be withdrawn were all cut up at Sendai General Depot, but one car (Green car 411-3) of the last set to be withdrawn, L3, was stored at the former Fukushima depot before being moved to Omiya in Saitama Prefecture in December 2017 where it is preserved at the Railway Museum.
Formation
The production 400 series sets were configured as shown below following the addition of a trailer car (car 15) in late 1995.
{| class="wikitable" style="text-align:center"
! Car No. !! style="background: #E6FFE6"| 11 !! style="background:#FFF2E6" | 12 !! style="background:#FFF2E6" | 13 !! style="background:#FFF2E6" | 14 !! style="background:#FFF2E6" | 15 !! 16 !! 17
|-
! Designation
| style="background: #F5FFF5"| Msc
| style="background:#FFF2E6" | M'
| style="background:#FFF2E6" | M
| style="background:#FFF2E6" | M'
| style="background:#FFF2E6" | T
| M
| M'c
|-
! Class
| style="background:#F5FFF5" |Green
| style="background:#FFF2E6" colspan="4" |Ordinary reserved
| colspan="2" |Ordinary nonreserved
|-
! Numbering
| style="background: #F5FFF5"| 411
| style="background:#FFF2E6" | 426-200
| style="background:#FFF2E6" | 425
| style="background:#FFF2E6" | 426
| style="background:#FFF2E6" | 429
| 425
| 422
|-
! Capacity
| style="background: #F5FFF5"| 20
| style="background:#FFF2E6" | 67
| style="background:#FFF2E6" | 60
| style="background:#FFF2E6" | 68
| style="background:#FFF2E6" | 64
| 64
| 56
|-
! Facilities
| style="background: #F5FFF5"| Toilet, wheelchair space
| style="background:#FFF2E6" | Payphone
| style="background:#FFF2E6" | Toilet, payphone
| style="background:#FFF2E6" | Luggage space
| style="background:#FFF2E6" | Toilet, luggage space
| Toilet, payphone
| Luggage space
|}
<gallery mode="nolines">
File:JREast-411-3.jpg|411-3 (car 11)
File:JREast-426-203.jpg|426-203 (car 12)
File:JREast-425-3.jpg|425-3 (car 13)
File:JREast-426-3.jpg|426-3 (car 14)
File:JREast-429-3.jpg|429-3 (car 15)
File:JREast-425-203.jpg|425-203 (car 16)
File:JREast-422-3.jpg|422-3 (car 17)
</gallery>
Fleet details
{| class="wikitable"
!Set No.
!Manufacturer
| Originally pre-series set S4, converted 29 June 1992.
|-
| L2
| rowspan="11" | Kawasaki
| 17 January 1992
| 20 November 1995
| 14 September 2001
| 7 October 2005
| 23 January 2009
|
|-
| L6
| 2 April 1992
| 8 December 1995
| 16 October 2001
| 24 December 2005
| 26 May 2009
Design
Exterior
thumb|Set L11 in its original livery in July 1997
The 400 series was originally painted medium silver-grey, with a darker roof and darkened areas around the cab windows and underframe. Between 1999 and 2001, the fleet was refurbished and repainted, adopting a revised livery featuring a higher area of dark bluish-grey on the lower body, rising to just below the side windows and separated from the silver-grey upper body by a green stripe. The dark grey treatment on the roof and around the cab windows was removed.
thumb|Set L1 at Omiya Station in June 2002, showing the door steps extended
Compared with the purpose-built high-speed Shinkansen lines, the Yamagata Shinkansen route is constrained by its legacy infrastructure. While the track gauge was widened, the original loading gauge was retained, requiring the 400 series to be designed with a narrower cross-section, leading to the "mini-Shinkansen" designation. When stopping at stations on the purpose-built high-speed Shinkansen lines, a retractable step flips up from beneath the doors to bridge the platform gap.
Interior
As a result of the narrower cross section, ordinary-class cars were fitted with 2+2 abreast seating, compared with the 3+2 configuration used on most Shinkansen trains. Green cars featured 2+1 abreast seating, compared with the 2+2 layout typical of other Shinkansen services. On subsequent mini-Shinkansen rolling stock, Green cars also adopted 2+2 seating, matching standard-class layouts. Seat pitch was in Green class (car 11), in reserved-seating cars (cars 12–15), and in non-reserved cars (cars 16 and 17).
During the life-extension refurbishment programme carried out between 1999 and 2001, the interiors were also upgraded with new moquette seat coverings. Green cars received blue moquette, reserved-seating cars received red moquette, and non-reserved seating cars were fitted with turquoise moquette.