One major way to transports goods and people across land is by train. It is efficient because trains can carry so much in one trip which allows less trips to complete a task. As time flies by, the train technology will increase their load capacity. For example, rail cars in the times between 1940 to 1950 were able to carry 180,000 pounds each car, and there used to be 60 cars on average. Now, many rail cars can take up 286,000 pounds and hold over 100 cars (Railway Capacity Background & Overview). This is a tremendous advance for railway technology, and it sure will keep going. A concern I have is the actual loading impact the rail cars have on infrastructure. As more weight can be put onto the rail cars, that weight will be distributed onto the railways and infrastructure under it and will damage the infrastructure which will lead to failure.
Some effects caused by train passage involve shear stress due to braking, actual weight, and vibrations due to speed. When a train is at a high speed and all of the sudden has to break, a braking force is needed to stop the train. This force will cause a shear stress onto the railways which will affect the steel the wheels have contact with. In addition, the weight the train puts onto the railway will cause normal and shear stress that will deform the steel and sub grade because of compression. With high speeds, the train will cause vibrations to occur and shake the soil around that leads to more deformation (Yang, Powrie, and Priest).
It does make sense to carry more with less trips to move items and people around, but this will make their loads much heavier. To be more efficient, the materials and infrastructure that withstand the amount loading and stress pay the price of deformation and reduction in performance. This effect increases even more if trains carry many rail cars behind it and will force infrastructure to perform at extreme levels. There has to be balance of the amount of weight trains carry because they can exceed a material’s capacity and lead to failure. At the same time, materials and infrastructure have to be designed so it can look into the future to expect large loads.
Railway Capacity Background & Overview. Retrieved November 14, 2014, from http://www.quorumcorp.net/Downloads/Papers/RailwayCapacityOverview.pdf
Yang, L., Powrie, W., and Priest, J. (2009). ”Dynamic Stress Analysis of a Ballasted Railway Track Bed during Train Passage.” J. Geotech. Geoenviron. Eng., 135(5), 680–689.