Collegues,
Whether we do real or imagined routes, we have to contend with things crossing over or under our efforts. Railroads you are familiar with may be (probably are) different so what I will mention here is what I learned at CSX. I was employed there as manager of the CAD systems in Engineering from 11/80 until I retired in 4/2001 and clearance diagrams were one of several items that were done on the CAD system. This was also during the period when double stack cars became the most common method of transporting containerized freight. So, the general rule was to have 27 feet between the rail head and the bottom of whatever went over the track, bridge, tunnel, water pipe, whatever. A meter is 3.28 feet, so we need at least 8.23 meters clearance. I round this up to 9 meters (29.5 feet) minimum on my routes. BUT this is to the bottom of whatever, so we have to add to that enough for the height of the beam, pipe, etc. For girder bridges, the rule of thumb is 1:10, i.e. a 60 foot girder needs 6 feet of height --- and if this is a deck girder supporting another track or road, then we should add another foot for ties etc. Thus when placing the road, or track, over the track, I will use 29.5+1+X where X is the girder height. Then divide the total by 3.28 to get the vertical space between tracks & tracks or roads in meters. If it is a road going under the track, often we can (in Google Earth) switch to ground view and just read the sign indicating clearance, if any. Some of these can be so low that fitting a automobile through them is like a bullet in a gun barrel. Little concrete tunnels were found often under L&N tracks, some with clearance as low as 8 feet, and often these were a single lane as well.
Jerry
Whether we do real or imagined routes, we have to contend with things crossing over or under our efforts. Railroads you are familiar with may be (probably are) different so what I will mention here is what I learned at CSX. I was employed there as manager of the CAD systems in Engineering from 11/80 until I retired in 4/2001 and clearance diagrams were one of several items that were done on the CAD system. This was also during the period when double stack cars became the most common method of transporting containerized freight. So, the general rule was to have 27 feet between the rail head and the bottom of whatever went over the track, bridge, tunnel, water pipe, whatever. A meter is 3.28 feet, so we need at least 8.23 meters clearance. I round this up to 9 meters (29.5 feet) minimum on my routes. BUT this is to the bottom of whatever, so we have to add to that enough for the height of the beam, pipe, etc. For girder bridges, the rule of thumb is 1:10, i.e. a 60 foot girder needs 6 feet of height --- and if this is a deck girder supporting another track or road, then we should add another foot for ties etc. Thus when placing the road, or track, over the track, I will use 29.5+1+X where X is the girder height. Then divide the total by 3.28 to get the vertical space between tracks & tracks or roads in meters. If it is a road going under the track, often we can (in Google Earth) switch to ground view and just read the sign indicating clearance, if any. Some of these can be so low that fitting a automobile through them is like a bullet in a gun barrel. Little concrete tunnels were found often under L&N tracks, some with clearance as low as 8 feet, and often these were a single lane as well.
Jerry
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