Rail transport can carry large and high-density commodities and bulk consignments over long distances at low cost. Rail transport is therefore well suited, to carrying raw materials and semi- finished goods, such as mining and agricultural products. In the bulk, long-distance transport market, throughput and price are more important to the client than transit time. For example, as long as stockpiles of iron ore or coal at a port are sufficient, the arrival times of individual trains are not important. However, in many transport segments, such as containers and break-bulk shipments, rail transport is losing ground in favour of road transport because road freight carriers offer regular, shorter and more consistent transit times.
Railways generally rely on a system of fixed infrastructure based on two parallel metal rails laid on supports known as ‘sleepers’ although mono-rail systems do exist. Railways require a solid base and must be constructed with relatively shallow gradients as well as wide radius curves. Rack and pinion systems may be installed to improve the operational restriction created by steep gradients but nevertheless the problem is a real one for railway engineers. In addition the rail track needs to be free from barriers to the uninterrupted forward progress of the train.
Therefore bridges, tunnels and crossing points for roads need to be constructed to allow an unimpeded passage for the train. In addition railways will require stations to allow the transfer of passengers or cargo from and to the train. A method of management for the trains’ operation is required to avoid collisions between trains operating at different speeds on the same section of track. This is achieved through a system of signaling and train scheduling.
Locomotives
Trains are powered by using motive units known as locomotives. Locomotives may either pull or push the train from the rear. In some cases two or three locomotives are used in a combined effort of pushing and pulling the train. Locomotives may be powered by diesel engines, electric power sourced from an overhead pantograph or power rail under the train, steam power, and in the case of monorail systems magnetic power.
Rolling stock
Rolling stock (in the USA these are referred to as ‘railcars’) is the collective name for the different types of vehicle drawn by the locomotive. The locomotive is coupled to the various pieces of rolling stock to form the train. The variety of rolling stock is diverse and reflects the different types of cargo being transported. Cargo may be transported in enclosed boxcars, refrigerated wagons, flat wagons, tankers, wagons adapted to carry containers (in some countries these may be double stacked), hoppers, and car transporters. Some trains are adapted to carry road vehicles that are driven on board and in some cases specially adapted road vehicles are coupled together to form the train. Passengers will be carried in carriages designed for the purpose.
Railway gauge
This is the distance between the two rails that comprise the railway.
- The standard gauge which is used in approximately 60 per cent of the world’s railways is 4’8″ wide.
- Broad gauge refers to rail widths greater than 4’8″. Some railways use 5’6″ rail width.
- Narrow gauge refers to rail widths less than 4’8″. Some railways use a 3’6″ rail width.
- Dual gauge railways have three or four rails positioned in such a way that different gauges may
- be utilized.
A break of gauge is the point at which two different gauges meet. This can oft en present problems at national frontiers where different gauges are used in the countries either side of the frontier. Broader rail gauges are capable of carrying heavier loads but utilize more land space and require broader curves in the rail track.
Loading gauge
This refers to maximum permitted height and width of the rolling stock that may be used on a given section of railway. The loading gauge will be a function of the height of overhead restrictions such as bridges and tunnels, which in turn restricts the effective operating height of the train. In addition the distance between train pathways and trackside structures will dictate the width of the rolling stock permitted.
