Question 2 For the planning and design of a new urban Metro rail system, and regarding the vertical track or rail alignment, what would be the desirable profile of the alignment on the approach and departure end of a railway station platforms and why? The Desirable profile of the alignment should be flat and straight as possible. This will allow trains to reduce their speed as they approach the platform and it will give the drivers a better vision of the track and provide them with enough time to brake if there is any disruption on the track. On the other hand, by keeping the track straight and flat will allow the passengers to board onto the train smoothly compared to an inclined platform. Having straight alignment at departure will smoothen the acceleration from 0 to a higher speed as the train leave the platform. Question 3 50% Outline your understanding of the following terms: 50% . Continuous Welded Rail - It is defined as rail that has been welded together to form lengths that are greater than 82m. This rail is been used in most modern railways, as it improves the driving characteristics of the track, increase comfort while increasing track speeds at lower driving resistance. The main disadvantage of continuously welded track is that, due to temperature changes, it got limited freedom of expansion and contraction of the rails. Therefore, the rail gets induced with large longitudinal forces which will result in rail deformation and lateral and longitudinal displacements of the track. · Flash Butt rail welding - This is an electrical resistance welding processes used to join rails together in a fully automated operation, where the energy transfer is provided primarily by the resistance heat from the part itself. · Aluminothermic rail welding - In Aluminothermic process, the rail end is joined together by pouring molten steel into a mould surround the gap between the rail. The rail ends are connected by the liquid metal. It is a chemical reaction between aluminium and iron oxide, which produces enough heat for melting the steel.
Question 4 Regarding train operations what is meant by the term 'Dwell Time'. Is the 'Dwell Time' for a High-Speed Rail (HSR) train stopping at a station likely to be shorter or longer than for a Metro train stopping at a station assuming that both trains are of comparable length? Dwell time is the time a train stands at a platform to allow passengers to 'detrain and 'entrain', along with door opening and closing process. There are other factors affecting the dwell time, which includes; number of carriages in a train, passengers' volume at the station, number of doors per train and many more. Dwell Time for high speed rail are shorter than metro trains because, high speed rail are mostly used for longer distance, hence it has smaller number of stops compared to metro which has more frequent stops meaning higher dwell time.