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When we talk about High-Performance Signalling, which, after all, is the subject and purpose of this newsletter column, we need to talk about how signaling can support the efficient driving of trains.

If you think this is a minor issue, think again.

If a heavy freight train running at, say, 80 km/h, needs to be stopped due to an insufficiently cleared signalling route, and then re-accelerates to the previous 80 km/h, the energy wasted by that stop-start manoeuvre could supply the entire energy budget of a mid-sized town for months. At least, that is what I heard from some energy experts who analyse things like this.

Stopping a passenger train from line speeds between 200 and 300 km/h might not burn just as much energy, but it sure is quite wasteful too.

This illustrates one of the problems of so-called conventional signalling with optical lineside signals. The train driver usually just sees one signal, which indicates the status of the next signal. A caution (usually yellow or amber) signal aspect means that the following signal shows red, so the train driver is obliged to bring the train to a full stop at that next signal, even if that signal may clear in the meantime. There are a few caveats to this, but bear with me for the sake of the argument.

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