DBAG Class 424. The Class 424 is a class of electric multiple units formerly used on the Hanover S-Bahn network. 16 units were reallocated for the Munich S-Bahn and 24 units for the Cologne S-Bahn.

Description 
The Class 424 are similar to Deutsche Bahn's Class 425 and Class 423 trainsets.

A Class 424 unit consists of four cars that share three jacobs bogies and can only be separated at maintenance facilities. The inner two cars are designated as Class 434. A 424 unit typically consists of the following cars, where x is the unit's number:
 424 x
 434 x
 434 (x+500)
 424 (x+500)
e.g. 424 037 + 434 037 + 434 537 + 424 537. Different consists usually occur when the remains of partially destroyed units are combined to form one intact EMU.

They have no visual distinctions to the Class 425. However, the Class 424 has a lower maximum speed of 140 km/h compared to the 160 km/h of the Class 425. Aside from that, installed on the Class 424 trains are variable steps and extendable platforms to reduce the gap between train and platform, which isn't fitted to earlier Class 425 units.

In comparison to the Class 423, the Class 424 feature a comparatively low floor height of  to allow step-free access on  platforms. They also lack a third set of doorways in the center of each car.

Operational History

S-Bahn Hannover
The Class 424 vehicles were supposed to start operation in the year 2000, which was then delayed due to technical issues. The transformers under the car body were not adequately protected and resulted in functional problems to the network signal and protection system. During the Expo 2000, borrowed Class 423 units from the Munich S-Bahn and Stuttgart S-Bahn were operated instead. 

During large events such as the Hannover Messe, the fleet is often supported by Class 425 units from other regions. Eventually, the fleet is then reinforced with Class 425.15 units for operation in the S5 to Paderborn. In 2008, The fleet was then completed with 13 Class 425 units of the 5th batch.

In the 12th of June, 2022, the operation of the Class 424 in Hanover ended, as operations of the Hanover S-Bahn net was handed over to SBH - S-Bahn Hannover.

Naming 

During their operation in Hanover, some of the units carry names of towns and cities on the Hanover S-Bahn network:

 424 001 Burgdorf
 424 002 Bückeburg
 424 004 Lehrte
 424 005 Wedemark
 424 006 Neustadt am Rübenberge (accidented, out of service)
 424 007 Bad Nenndorf
 424 011 Stadthagen
 424 014 Springe
 424 017 Bad Münder am Deister
 424 018 Celle
 424 019 Minden
 424 021 Wunstorf
 424 024 Seelze
 424 025 Nienburg/Weser
 424 027 Hannover
 424 032 Bad Pyrmont
 424 033 Hameln
 424 035 Haste (accidented, out of service)
 424 037 Langenhagen
 424 038 Barsinghausen
 424 039 Ronnenberg

Munich S-Bahn

To facilitate an increase of service on some lines, the Munich S-Bahn took over 16 vehicles from Hanover. The vehicles were planned to operate by autumn of 2022, which was subsequently delay, as the trains should be refitted and modernized before operation in Munich. The first vehicles started operation by autumn of 2023.

The vehicles are modernized with new passenger information displays in the form of 8 double facing monitors throughout the interior. 8 outward facing LED displays are fitted to the side vehicles and 2 on each end of the train. The seats were given the same colour as modernized class 423 units in Munich. WiFi service was added to the trains as well. Lastly, the toilets were removed to make way for a larger multiple-purpose area.

As the vehicles have a floor height difference of about 80 centimeters to the Class 423 (to which platform heights were built for), the Class 424 trains are only operated outside the Stammstrecke as shuttle and complementary rush hour services between Dachau & Altomünster (S20) and Geltendorf/Buchenau & the main station (S4). The Class 424 are also not fitted with necessary protection system that is needed to operate within the Stammstrecke.

Cologne S-Bahn

The role of the class 424 in the Cologne S-Bahn network is to replace aging class 420 units. The 24 units for Cologne underwent a redesign process by internal DB workshops in Krefeld and Hanover as well as by Vossloh Rolling Stock in Kiel. The vehicles were given a new colour scheme internally and externally. The livery is made to somewhat resemble that of the Cologne Stadtbahn, while the seat padding were given a turquoise colour. The units also feature new facilities such as new passenger information displays, outward facing LED displays and WiFi service, similar to Munich units. Unlike Munich units, the Cologne units also feature power outlets.

In December 2023, the modernization project received a special mention from the German Design Award 2024 in the category of "Aviation, Maritime and Railway".

The modernized vehicles were unveiled to the public in April 2024. The vehicles are planned to operate on lines S11, S12 and S68. Stations on these lines does not have uniform platform heights, being either 760 mm and 960 mm. Passengers will have an even entrance for the former and must take a step for the latter. 

Electric multiple units of Germany
Hanover S-Bahn
15 kV AC multiple units
Bombardier Transportation multiple units
Siemens multiple units
Train-related introductions in 1998