Transportation Engineering: Characteristics Of Rail Transport

Rail transport is the most important medium of transportation across the globe. Railways not only carry passengers, but they also carry goods, emergency services, and army equipment. This article covers the major characteristics of railway transportation.

Railways came into existence as early as 6 B.C. The first railway track was 6 kilometers long and it was used for the transportation of boats. However, the turning point for railways and railway technology was the invention of the steam engine by James Watt in 1775. Since then, railways have undergone huge changes across the globe. Today we have metro rails speeding as fast as 300 kmph. China has constructed the highest rail road of the world in the Tibetan region. Even the railway tracks have changed and today we have reliable, durable, and advanced rails, which make journey by train even more economical and efficient.

Railway Tracks

Rail track mainly comprises two steel rails that are parallel and fixed perpendicular to the elements known as railway sleepers, the purpose of which, whether made of wood, steel, or concrete, is to keep a constant distance between the tracks, the track directs the flanged wheels of the cars on the desired direction without much steering effort. The tracks allow the trains to be significantly longer compared to road transport. The rails and the sleepers are placed on compressed earth foundations. It is ensured that the load of rails and sleepers is evenly distributed on the foundations to avoid the track buckling. 

Vibration monitoring is essential to ensure the stability of the train, rails, and the rail foundations. There are several ways to relieve stress in the welded segments. The railway track geometry should be carefully analyzed before the laying of rails and the railway sleepers. The foundation ground is likely to be settled with the passage of time, and also due to the heavy vehicle weight. The rails are subjected to extensive stresses due to which the material selected is good quality alloy steel, and the rails have expansion joints for temperature variations. The more the weight of the rails and other components, the faster can be the trains.

Track Components

The railway track is a complex composition of rails, sleepers, and fasteners installed on hard foundations. This complicated configuration is like other structures that are firmly embedded in the ground. Rail track may be believed to be hovering on the ground foundation. Therefore, the study and analysis of track stresses is complicated and important for the track safety. The rail track can be assembled at the site or prefabricated. The outward rail is higher compared to the inner side rail on the curves. This technique is called super elevation, and it decreases the forces that tend to dislocate the track. The ride is also made comfortable by this process. The track is designed to endure the static and dynamic wheel loads and disperse them to the ground. The superstructure will be affected partially due to the high train speeds, but will attain the original configuration when the load is released. The elements of the railway track are subjected to different loads as the train moves on the rails. These stresses are determined by considering the track as an elastic structure.

Continuous Welded Rail

Continuous welded rail, as used in modern rail systems, is also called ribbon rail. In this type of track, flash butt welding is used to weld the rails together. Flash butt welding requires an automatic track laying mechanism with a strong electric current. The color of the ends becomes white hot because of the electrical resistance, and then they are joined with each other creating a strong weld. A continuous rail can be some kilometers long. The continuous welded rail segments are repaired by thermite welding. Since the joints are few, this track is extremely durable, needs less maintenance, and the ride is smooth. The trains can attain high speeds with little friction. The laying of welded rails is expensive compared to the jointed tracks. If not controlled, the rails would elongate during the hot weather and contract during the cold weather. The rail movement with respect to the sleeper is controlled by using anchors or clips. Anchors are generally used for wood sleepers, while clips are used to fasten concrete and steel sleepers. If the longitudinal and lateral rail controls are inadequate, the track will change its configuration with changes in temperature, which may cause a derailment.

Changes in technology and increases in passenger load have resulted in the abandonment of thousands of miles of railway tracks in the US. Some of the railway tracks have been upgraded and those which could not be upgraded have been abandoned by the government and railway companies because of security issues.

Modern Railway History Time-line

• James Watt invented the Steam Engine in 1775
• Oliver Evans develops American steam engine in 1800 and in 1804 he successfully installs it in a boat.
• The Mumbles Train runs as world's first passenger train in 1807
• First eight-wheeled engine South Carolina was built in 1831.
• President Abraham Lincoln signs the Pacific Railway Act in 1862.
• The first diesel-electric locomotive comes into the picture in 1918.
• High speed rails come into existence in early 1960s.
• Shanghai Metro System becomes world's largest urban transit system in 2010.