Indian Railways consider their Schedule of Dimensions (IR-SoD-2004) as sacrosanct. They do not deviate, so it is said, from the prescribed dimensions. If any deviation is to be made, they have to approach their Research Design Standards Organisation at Lucknow (RDSO). As per IR-SoD-2004, the floor of the new rakes are to be at 1,200 mm from Top of Rail (ToR) and the Platform level at the coping (edge) between 760 mm to 840 mm. For the older rakes, the floor levels vary from 1,345 mm at empty condition and 1,200 mm at fully loaded condition.
The older rakes have coil springs as suspension while the newer rakes have pneumatic suspension, as they have in Metro rail coaches. Pneumatic suspension compresses additional air into the air cylinder to take up extra load and maintain the coach floor level constant. Thus, the ‘official’ vertical gap from the platform for new rakes would vary from 360 mm to 440 mm. For the old rake, this would be between 360 mm and 585 mm.
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