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I read that trains in pratice instead of acceleration to a certain speed level and holding the speed, they accelerate and then cost, accelerate again, und keep this pattern. This was shown by experiments. What is the explanation why this way of driving is more energy-efficient?

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  • $\begingroup$ Do you mean internal combustion engine powered rather than electric trains? $\endgroup$ – Transistor Sep 18 '17 at 17:41
  • $\begingroup$ Please provide references for this claim. $\endgroup$ – Carl Witthoft Sep 18 '17 at 18:09
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Just keeping a train at a fixed speed over level terrain takes a small fraction of the engine's power output. As a result, the engine runs very inefficiently.

In pulse and glide, the short bursts from the engine during the pulse phase are much higher power. These allow the engine to run at higher efficiency.

Roughly the same overall average power is produced by the engine either way, but with pulse and glide, that power is produced at a more efficient operating point of the engine.

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  • $\begingroup$ This may be true for direct-drive ICE locomotives but I don't think either direct electric or diesel-electrics are subject to this efficiency curve. $\endgroup$ – Carl Witthoft Sep 18 '17 at 18:11
  • $\begingroup$ @Carl: In diesel-electric, the ICE still runs as needed. The electric part is more as a replacement for variable gearing and to help distribute the power from the ICE to the wheels. There is also effectively no electrical storage. All the power comes from the ICE within a short time. When the train is running along at steady speed on level terrain, the ICE is still being used at a small fraction of its rated output. The gearing gives you a choice over the torque/speed tradeoff, but not the power. $\endgroup$ – Olin Lathrop Sep 18 '17 at 18:22

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