Why Does the TGV Reach 320kph While the Shinkansen is Limited to 280-300kph?

The primary factors contributing to the difference in maximum speeds between the TGV (Train à Grande Vitesse) and the Shinkansen, Japan's famous high-speed rail system, involve a complex interplay of engineering, infrastructure, and operational practices. While it is often suggested that the width of the trains is a contributing factor, this misconception highlights the need to explore other critical elements that influence speed capabilities.

Factors Affecting Speed

Aerodynamics

The design of the TGV is optimized for aerodynamics, enabling it to achieve higher speeds more efficiently. Aerodynamic shapes help to reduce drag, which is crucial for maintaining and increasing its speed. In contrast, the Shinkansen, while not lacking in design optimization, may not have been designed as aerodynamically as the TGV, leading to differences in performance at high speeds.

Track Design

The quality and characteristics of the track are essential for high-speed rail operations. The TGV operates on specially designed tracks that are tailored to support higher speeds. These tracks often feature better curvature and higher elevations, which contribute to the overall efficiency of the train's operation. The Shinkansen, operating on the standard 1435 mm track gauge, also benefits from careful track design, but the exact specifications and accommodations may differ.

Rolling Stock Design

The design and engineering of the train cars, including aspects like weight distribution, suspension systems, and braking technology, are integral to achieving high speeds. TGV trains are exceptionally engineered for high-speed travel, with features tailored to enhance performance and safety at top speeds. In comparison, the Shinkansen, while highly reliable and efficient, may have different design priorities that can affect its speed capabilities.

Safety Regulations

Different countries have varying safety standards and regulations that impact the maximum allowable speeds. The Shinkansen is renowned for its strong focus on safety, passenger comfort, and reliability. This prioritization can sometimes limit speed to ensure the highest levels of safety. TGV, on the other hand, may have different operational practices that allow for higher speeds under certain conditions.

Operational Practices

The operational strategies of the rail systems also play a role. Speed limits can be set based on specific routes and conditions, affecting the maximum speeds that trains can achieve. The operational practices of TGV are more flexible, allowing trains to switch between dedicated high-speed lines and the classic network, providing greater operational flexibility.

Width Considerations

It is important to note that while the Shinkansen is indeed wider (approximately 3.4 meters) compared to the TGVs (2.9 meters), this difference alone does not directly cause the speed disparity. Wider trains can offer certain stability benefits, but they also tend to face more aerodynamic drag due to their larger profile. Therefore, the impact of train width on speed is not as straightforward as it might seem.

On some sections of track, both trains operate at 320 km/h, such as on three sections of track in the east and southeast of France, and in the northern Japanese Shinkansen lines. These speeds are determined by economic choices, track profile, and signaling systems. The ability to operate at higher speeds on these specific tracks underscores the adaptability of the TGV and the design constraints of the Shinkansen.

Differences in Rail Network Designs

A train's size and operational capabilities are also determined by the track gauge and loading gauge. The track gauge is the width between the paralleled running rails, while the loading gauge defines the dimensions based on line-side obstructions, including bridges and station platforms. The standard 1435 mm track gauge used by the Shinkansen allows for wider trains and dedicated high-speed lines, unlike the 1067 mm narrow gauge used in Japan for classic lines.

The Japanese network has two separate and incompatible national rail networks, each with its own gauge, leading to logistical challenges. France, on the other hand, maintains the same national rail track gauge, allowing TGV trains to switch between dedicated high-speed lines and the classic network, providing greater operational flexibility.

In conclusion, the difference in speeds between the TGV and the Shinkansen is a result of a combination of design, engineering, and operational factors. While the width of the trains is a factor in operational design, other critical elements like aerodynamics, track design, safety regulations, and operational practices play equally important roles in determining optimal speeds for high-speed rail systems.