Railroads - Components, construction and maintenance

The invention of the wheel dates back to 3,500 BC. While the wheel's ability to roll over the ground represents a considerable advance in human activity, it also presents a major constraint due to its very small contact surface. The Romans compensated for this disadvantage by building tracks in hard materials, and even by creating ruts to prevent transverse skidding. Two fundamental concepts thus took shape: distributed load support and load guidance.

The 16th century brought a solution to this problem: two wheels combined to form an axle ran on a track made of two parallel wooden profiles, spreading the load over the ground to prevent the axle from getting bogged down. The two profiles guide the axle. The oldest reproduction of a track dates back to 1550, and shows a wagon being pushed by a miner in the Leberthal mine in Alsace.

In 1738, at the Whitehaven mines in Great Britain, the track was perfected, and the wooden profiles were covered with metal plates. Reynolds introduced the first all-cast-iron "rails" in 1763. In 1804, Trevithick built the first track-bound "locomotive", applying Denis Papin's theory of steam energy (1671). Human and animal energy was replaced by steam power, enabling heavy loads to be hauled at much higher speeds.

Railroads thus became the first high-capacity land transport system. Track technology, ensuring load distribution and guidance, enabled the creation of convoys of numerous vehicles, coupled together and called "trains".

In the railway system, infrastructure is the fundamental component in the truest sense of the word, like water for maritime transport or air for air transport. Railroads are the key players. It enabled transport capacities to be constantly increased, from 100 to 3,000 tonnes; axle loads were raised to 20, even 30 tonnes; and in 1955, rail speeds of 331 km/h were reached in France. But it was also subject to all the constraints of the rail industry, including terrain and climate. Nevertheless, this infrastructure remains the essential interface between the ground and the rolling stock, whose performance and safety it must guarantee.

We analyze the track's main functions and constraint functions to describe each of the components capable of satisfying the result. The major developments of the last few decades are noted, to justify the current results of railway operations and the adaptation of the track to other operations as different as urban transport or high speed.

It's worth noting that developments and advances in track technology are at least as important as those in rolling stock. In fact, the two are so closely linked that ongoing dialogue is essential between those involved in these two components of rail...