Class 458 Juniper Alstom Birmingham Electric Multiple Units (EMUs)

Class 458 were built by Alstom Birmingham from 1998-2000 and work off third rail 750 V DC power supply.  Class 458 EMU units are constructed of steel. Class 458 trains were designed for outer suburban work.  Class 458 4-car units have a maximum speed of 100 mph. South West trains use all of these Class 458 EMU sets.

A history of the Class 458 EMUs

[Author & photographer © Dr Phil Brown PhD (plus text help from AI these days), page updated May 6th 2026]

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Class 458 EMU 8008 train-set (2 x Class 458 4-car set units) in the depot sidings near Clapham Junction.

Some Class 458 EMU units, carriages 67601 and 74101 from set 8001, amongst those being refurbished at WabTec Rail Limited, Doncaster (July 2015)

A history of the Class 458 EMUs

The Class 458 “Juniper” EMUs are Alstom‑built suburban/inter‑urban units introduced from 2000 on the South Western network, notable for a troubled early service life, a major mid‑life rebuild, and a second full refurbishment completed in 2024.

Below is a full, structured history grounded in authoritative sources.

Origins and Ordering of the Class 458 EMUs (1996–1998)

South West Trains inherited a large fleet of ageing slam‑door EMUs in 1996. To begin replacing them, SWT issued a tender in November 1996 for 30 new air‑conditioned 4‑car EMUs. In 1997, SWT and Porterbrook awarded Alstom a £90 million contract for what became the Class 458 fleet.

Construction took place at Washwood Heath (Birmingham) and Barcelona, with the first unit delivered in October 1998.

Design and Technical Features of the Class 458 EMUs

The Class 458 belongs to the Alstom Coradia Juniper family. Key characteristics include:

• 4‑car formation as built (DMCO–TSO–MSO–DMCO)
• Steel bodyshell
• 750 V DC third‑rail supply
• Alstom ONIX 800 IGBT traction
• 6 × 270 kW motors (2 per motor car)
• 100 mph maximum speed
• Sliding plug doors
• Regenerative and disc braking

These units were intended for Waterloo–Reading and other outer‑suburban services.

Early Service Problems of the Class 458 EMUs (2000–2003)

The first units entered service on 25 February 2000, but introduction was slow and problematic. Issues included:

• Air‑conditioning failures
• Bogie ride‑quality problems
• Faulty corridor connections
• Driver computer system faults

At one point, only two units were available for service.

In September 2000, all Juniper‑family units (Classes 334, 175, 458) were temporarily banned after two runaway incidents involving other Juniper types.

Full fleet entry into service was not achieved until 2003.

Mid‑Life Rebuild: The Class 458/5 Programme (2013–2016)

To increase capacity into London Waterloo, SWT merged the Class 458 fleet with the mechanically similar Class 460 “Gatwick Express” units.

• 30 original 458/0 units + 6 converted 460s = 36 five‑car 458/5 units
• Rebuild carried out 2013–2016
• New formation: 5‑car, with updated interiors and revised cab ends

This programme created the 458/5 subclass and increased seating capacity.

Operational Use of the Class 458 EMUs

The Class 458 fleet has been used on:

• Waterloo–Reading
• Waterloo–Windsor
• Waterloo suburban services
• Limited long‑distance services (planned Portsmouth Direct deployment was later abandoned)

They are maintained at Bournemouth depot.

2022–2024 Refurbishment of the Class 458 EMUs

A major refurbishment programme funded by Porterbrook and carried out by Alstom at Widnes and Crewe upgraded 28 four‑car units (458/4 subclass).
Upgrades included:

• New seating (234 seats per 4‑car set)
• Charging points and wireless‑charging tables
• New carpets and interior refresh
• Improved acceleration
• Increase of top speed from 75 mph to 100 mph after wheelset overhaul
• New SWR livery

The final refurbished unit (458414) was completed in December 2024.

Current Status of the Class 458 EMUs (2025–2026)

• 28 units remain in service with South Western Railway.
• They are expected to be replaced by the Class 701 Arterio fleet, though delays mean the 458s continue to operate.

⭐ Significance of the Class 458 EMUs

• One of the first modern AC‑traction third‑rail EMUs on the SW network
• A fleet that overcame severe early reliability issues
• A rare example of two EMU classes (458 + 460) being merged into a single rebuilt fleet
• Continues to serve after two major refurbishment cycles

If you’d like, I can also produce a 458/0 vs 458/4 vs 458/5 comparison table, or a timeline diagram of the fleet’s development.

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See Also * Class 01 * Class 02 * Class 03 * Class 04 * Class 08 * Class 09 * Class 10 * Class 11 * Class 14 * Class 20 * Class 24 * Class 25 * Class 26 * Class 27 * Class 31 * Class 33 * Class 37 * Class 40 * Class 43 * Class 44 * Class 45 * Class 47 * Class 50 * Class 52 * Class 55 * Class 56 * Class 57 * Class 58 *  Class 60 * Class 66 * Class 67 * Class 68 * Class 70 * Class 71 * Class 73 * Class 76 * Class 77 * Class 86 * Class 87 * Class 90 * Class 91 * Class 92 * Class 101 * Class 108 * Class 114 * Class 117 * Class 121 * Class 127 * Class 141 * Class 142 * Class 144 * Class 150 * Class 153 * Class 155 * Class 156 * Class 158 * Class 159 * Class 165 * Class 166 * Class 170 * Class 175 * Class 180 * Class 185 * Class 220 * Class 221 * Class 222 * Class 252 * Class 313 * Class 315 * Class 317 * Class 319 * Class 320 * Class 321 * Class 322 * Class 323 * Class 325 * Class 332 * Class 333 * Class 334 * Class 350 * Class 357 * Class 360 * Class 365 * Class 373 * Class 375 * Class 376 * Class 377 * Class 378 * Class 379 * Class 380 * Class 387 * Class 390 * Class 395 * Class 414 * Class 423 * Class 442 * Class 444 * Class 450 * Class 455 * Class 458 * Class 460 * Class 465 * Class 466 * Class 507/508 * Class 3000 *

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