What is the Minimum Speed for a Train to Be Considered High Speed?

The definition of what constitutes a high-speed train can vary depending on the country and specific rail systems. Generally, trains are deemed high-speed if they can achieve speeds of at least 250 kilometers per hour (155 miles per hour) on dedicated tracks. For those operating on conventional tracks, this threshold is around 200 kilometers per hour (124 miles per hour).

The Widely Accepted Benchmarks

However, the debate on the minimum speed is more nuanced. While 200 km/h is often cited as the minimum for a high-speed train, this threshold can be exceeded depending on the specific circumstances. For instance, some locomotive-hauled passenger trains feature slightly updated rolling stock that can reach 200 km/h, even though they may still have traditional features like opening windows and non-enclosed toilet systems. These trains typically have modifications to the bogies and brakes to allow for higher speeds.

Investment and Infrastructure Play a Major Role

Trains that operate at speeds consistently above 200 km/h often have airtight bodies, closed toilet systems, and are typically run on newly built dedicated high-speed lines where they don’t mix with general traffic. The significant investments involved in these high-speed lines often result in trains operating at even higher speeds, such as 230 km/h or more, sometimes reaching a common benchmark of 250 km/h. This is due to the enhanced safety and operational efficiency provided by modern signaling and infrastructure.

The Role of Signaling in High-Speed Operations

The signaling system plays a crucial role in determining train speeds. General railway industry practice indicates that speeds above 200 km/h require a different signaling approach. Most railway tracks use fixed signals similar to road traffic lights, providing colored visual cues for the driver regarding the track conditions ahead. These signals, however, are not suitable for speeds above 200 km/h due to the risk of driver impairment and reduced reaction time.

For trains operating at or above 200 km/h, the driver receives a continuous update of track conditions in the form of a target speed indicator in the cab display. This system ensures that the train travels at high speeds with the necessary safety measures. In addition, there are high-visibility line-side markers for further reference.

Exceptions and Adaptations

There are a few notable exceptions, such as in France and the UK, where line-side signaling systems have been adapted to permit travel above 200 km/h along traditional tracks. In France, between Tours and Bordeaux, TGV trains previously ran on classic tracks with some sections upgraded for 220 km/h. They employed an innovative double-block system, allowing authorized speeds up to 220 km/h. However, this system is now redundant as TGV trains now use a parallel high-speed track and cab display signaling, allowing operations at 300 km/h.

In the UK, a special flashing green light was added to the line signals between Grantham and Peterborough, authorizing the driver to take the train to 225 km/h. This is used by commercial passenger operations, and trains travel at the line’s general ruling speed of 200 km/h.

In conclusion, the minimum speed for a train to be considered high-speed is more of a guideline than a hard and fast rule. The critical factors are not just the speed itself but also the signaling, infrastructure, and operational requirements. Understanding these nuances is essential for anyone interested in high-speed rail systems worldwide.