Note: this page is for educational purposes only. It is not a substitute for the official page of the operating company or manufacturer.
Railway infrastructure is the key element that enables trains to travel in one direction or another. It is the basis of the term ‘railway’, since railway infrastructure has always consisted of one or more tracks made up of two metal rails that serve as a guide for the rail vehicle. As the track network expanded, the railway was equipped with signalling to make trains safe and monitor traffic. Later, in the 1920s and 1930s, an electric wire was installed above the tracks to supply power to the locomotives. Today, the track remains much the same as it was 200 years ago, with four sub-elements:
Civil engineering:
• Track bed
• Bridges and viaducts
• Tunnels
Railway track:
• A brief history of the track
• Ballast
• The rails
• Sleepers et fixings
• Rail gauge
• UIC classification
• Cant deficiency
• Switches
• Maintenance
• Slab track
Signalling:
• Basic
• Conventional signalling
• Signalling
• Train detection
• Traffic control center
• ERTMS / ETCS
• from GSM-R to FRMCS
Electrification:
• Four common voltages
• Electrical substations
• Traction current
• Energy consumption
The railway, a complex environment
Infrastructure is the very basis of the railway concept. A little over two centuries ago, the railways began to differ from the dirt and stone roads that formed the only land-based transport network at the time, alongside inland waterways of course. The main difference between the railways and these other forms of transport was two fundamental innovations:
• the support, which was now made of iron, but which was relatively expensive;
• the concept of guidance, which prevents the vehicle from going off the rails, provided that the two supporting guides – in this case the rails – are firmly maintained at a strict distance from each other along the track.
On the other hand, the vehicle’s method of travel is no different from that of other forms of transport: it’s still the good old wheel. The innovative concept of the ‘ guided railway ’ – steel wheels on steel rails – led to the implementation of a special design for the railway network. Why did this happen? Because the wheel-rail-iron contact is much less adhesive than the contact between the wood of horse-drawn carriages and the stone of the time, or today between rubber and bitumen. On the rail, the wheel glides better and has very little resistance: this is a strength, but it’s also a weakness.
Its strength lies in the fact that, with very little effort, it can move a set of vehicles that are hooked together: the train. This train can be very heavy and long, which is an advantage over land transport, where only short vehicles travel. The guidance provided by two rails prevents vehicles from deviating from their trajectory. As for the weakness of the steel wheel-rail, it has a name:grip. Lack of grip is a problem when starting off, but it is also a problem when braking trains, especially when they are heavy. This is why specific civil engineering criteria had to be devised:
• the track must be as shallow and straight as possible;
• curves must have a large radius, depending on the speed envisaged at the time of construction;
• where the terrain is difficult, bridges and tunnels must be built to avoid excessively steep gradients;
Guided transport makes it impossible to avoid an obstacle. This is why, from the very beginning of the railway, it was necessary to warn the train behind what was happening in front: this is the role of signalling. The signal protects the train in front by telling the train behind not to cross the signal as long as the train in front is still present on a section X of the track. This design has made it compulsory to monitor traffic 24 hours a day, which is also a costly proposition.
The locomotive was invented in England in 1825. It used the leading energy source of the time: coal. This fuel, burnt on board, was used to boil water, which, transformed into steam, was used to drive the wheels by means of pistons. Electricity first appeared on a train at the Berlin World Fair in 1880. However, it was not until the 1920s and 1930s that the first applications of electric motor traction were seen on a real locomotive. This new energy radically changed the conditions of rail traction:
• For the first time, the locomotive no longer carried its own fuel or produced its own energy on board, as the steam locomotive did, but instead harnessed its energy directly, without any transformation, via an overhead wire called a catenary;
• The railways then gave up supplying polluting coal, which had an impact on the mines, and turned to suppliers of electricity, which is now recognised as green energy, which is not insignificant.
• To be optimal, a train service needs to find a catenary on as many railway lines as possible, which has led to heavy electrification work, using a wire supported by poles set up every 60m or so.
Modern railway infrastructure consists of a track laid on a platform whose civil engineering avoids steep gradients and curves. The rails are kept at a constant millimetre gauge by concrete sleepers, which are themselves laid on a bed of ballast (pebbles). The power required by the locomotive is either diesel or, above all, electric, thanks to a catenary suspended in the centre line of each track. The whole system is managed from remote command posts, which monitor the progress of traffic using signals located every X kilometres. Railway infrastructure combines civil engineering, steel and industrial electronics and electricity. These are very expensive and capital-intensive sectors, but when combined and managed well, they can offer the railways advantages in terms of traffic capacity and sustainable transport. 🟧
——————————————————————————————————————————————————————————————-