Why are Jacobs bogies safer in a crash?

Jacobs bogies significantly reduce the risk of 'jackknifing' (where train cars zig-zag and pile up) during a derailment. Because the cars are pinned together at a shared pivot point, the train tends to stay upright and aligned, reducing structural damage and passenger injury.

Which trains use Jacobs bogies?

Jacobs bogies are famous for their use on the French TGV and the Eurostar e300 series. They are also commonly found on modern tramways, light rail vehicles, and some commuter trains like the Stadler FLIRT.

What is the disadvantage of a Jacobs bogie?

The main disadvantage is maintenance inflexibility. Since the bogie connects two cars, individual carriages cannot be easily uncoupled or swapped out. The entire train must be lifted simultaneously in a workshop to separate the cars.

The Joint of Speed: How Jacobs Bogies Revolutionized Articulated Trains

Q: What is a Jacobs bogie?

A Jacobs bogie is a shared railway bogie placed between two carriages in an articulated train. It supports the ends of both vehicles, linking them together mechanically, rather than each vehicle having its own pair of bogies.

Why do high-speed trains like the TGV share wheels between cars? Uncover the engineering of the Jacobs Bogie, the key to stability and anti-jackknifing safety.

The Joint of Speed: How Jacobs Bogies Revolutionized Articulated Trains

December 10, 2025 1:09 pm

What is a Jacobs Bogie?

A Jacobs Bogie (named after Wilhelm Jakobs) is a specialized type of railway bogie found on articulated trains. Unlike conventional trains where each carriage sits on two of its own bogies, a Jacobs bogie is positioned between two carriages, supporting the rear end of one and the front end of the next. This design mechanically links the cars together, creating a semi-permanent “trainset” unit.

The Safety Advantage: Anti-Jackknifing

The most critical feature of the Jacobs bogie is its contribution to safety during a derailment. In a conventional train, derailed cars can split apart and zig-zag (accordion), a phenomenon known as jackknifing.

With Jacobs bogies, the carriages are physically pinned together at the pivot point. This rigidity forces the train to remain aligned as a single tube, even if it leaves the tracks. This characteristic is a primary reason why high-speed trains like the TGV and Eurostar have historically had high survival rates in derailment incidents.

Comparison: Jacobs Bogie vs. Conventional Bogie

The choice between using shared bogies or independent bogies defines the architecture of the train.

Feature	Jacobs Bogie (Articulated)	Conventional Bogie
Wheel Placement	Located between two carriages.	Located under the carriage body.
Weight	Lighter (fewer bogies per train).	Heavier (2 bogies per car).
Ride Comfort	High (wheels are not under seats).	Variable (noise directly under seats).
Flexibility	Low: Cars cannot be easily separated.	High: Cars can be coupled/uncoupled easily.
Axle Load	Higher (supports weight of two car ends).	Lower (load distributed over more axles).

Operational Challenges

While they offer superior aerodynamics and safety, Jacobs bogies present maintenance challenges. A train cannot be easily split in a depot; to remove a single carriage, the entire trainset must be lifted using synchronized jacks. Consequently, articulated trains are typically treated as fixed-formation units that rarely change length.