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Re: Half-a**ed-article on the errors of BART Technology
Author: Max Wyss
Date: 03-28-2016 - 01:56
Of course, now, 50 years later, we know more, and in retrospect, it is easy to moan about errors and wrong decisions. So, from today's points of view, a few thoughts:
• Gauge… an inconenience that it is not standard gauge, but that's about it. Rolling stock makers nowadays have their base kits allowing quick modifications, such as gauge.
• Voltage… a design decision; on the low side for a system with long lines; 1500 V (a reasonable maximum for third rail) would have reduced the numbers of substations. Overhead wiring would have increased the diameter of the bores of the tunnels… therefore more expensive.
• Rubber-tyred, à la Alsthom… in Paris, the noise issue was/is quite important, because of the extensive elevated lines. Also, we should not forget that there was non-neglectable (political) pressure by a big company headquartered in Clermont-Ferrand. Rubber-tyred metros have very good acceleration, and can very well deal with steep grades (average grade of M2 in Lausanne is something around 11%, if I remember correctly). However, there are weight limitations, asking for short carbodies, and speed can not be that high (in Paris, it is 60 km/h). So, not the best choice for Bart
• Wheel profile… hunting is controlled nowadays by more simulations (essentially unknown or awkward and expensive at the time) leading to an optimized wheelbase, and by applying dampers. But that all got developed later. I guess when the hunting got discovered, it was way too late to increase the wheelbase of the trucks.
• Wheel material combination… for that, I can not really follow the decisions, but I don't have enough material at hand showing how they came to it.
• S-Bahn philosophy… came later, although BART (nowadays) is some kind of mixture between S-Bahn and Metro.
So, the question is, what to do after those 50 years. Tear off and rebuild? Very expensive and time consuming.
Although, one thing which could be thought about would be in connection with a second tunnel: Cut back the "old" BART to an inner area, and make it a more complete Metro. Build the second tunnel standard gauge and build standard gauge lines connecting to the end point of the "Metro BART", and regauge the outer branches. Then operate the outer branch trains as express in the inner area. This too would be expensive, but less so than a complete overhaul.
Another thing not to forget is that the tunnel(s) will reach end of life in some 40 to 60 years.
• Gauge… an inconenience that it is not standard gauge, but that's about it. Rolling stock makers nowadays have their base kits allowing quick modifications, such as gauge.
• Voltage… a design decision; on the low side for a system with long lines; 1500 V (a reasonable maximum for third rail) would have reduced the numbers of substations. Overhead wiring would have increased the diameter of the bores of the tunnels… therefore more expensive.
• Rubber-tyred, à la Alsthom… in Paris, the noise issue was/is quite important, because of the extensive elevated lines. Also, we should not forget that there was non-neglectable (political) pressure by a big company headquartered in Clermont-Ferrand. Rubber-tyred metros have very good acceleration, and can very well deal with steep grades (average grade of M2 in Lausanne is something around 11%, if I remember correctly). However, there are weight limitations, asking for short carbodies, and speed can not be that high (in Paris, it is 60 km/h). So, not the best choice for Bart
• Wheel profile… hunting is controlled nowadays by more simulations (essentially unknown or awkward and expensive at the time) leading to an optimized wheelbase, and by applying dampers. But that all got developed later. I guess when the hunting got discovered, it was way too late to increase the wheelbase of the trucks.
• Wheel material combination… for that, I can not really follow the decisions, but I don't have enough material at hand showing how they came to it.
• S-Bahn philosophy… came later, although BART (nowadays) is some kind of mixture between S-Bahn and Metro.
So, the question is, what to do after those 50 years. Tear off and rebuild? Very expensive and time consuming.
Although, one thing which could be thought about would be in connection with a second tunnel: Cut back the "old" BART to an inner area, and make it a more complete Metro. Build the second tunnel standard gauge and build standard gauge lines connecting to the end point of the "Metro BART", and regauge the outer branches. Then operate the outer branch trains as express in the inner area. This too would be expensive, but less so than a complete overhaul.
Another thing not to forget is that the tunnel(s) will reach end of life in some 40 to 60 years.
