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The difficulty is that traffic lights are rather unpredictable. Some actually require you to speed up to the limit if you want to keep up with the wave. And o

The difficulty is that traffic lights are rather unpredictable. Some actually require you to speed up to the limit if you want to keep up with the wave. And others won't light up until you pass a sensor so coasting and regulating speed far ahead doesn't work. Others still may be triggered by sensors on crossing traffic, whether you get a green or red is unknowable. I'm guessing the signals on railways are much more predictable.

globular-toast 5y ago
> I'm guessing the signals on railways are much more predictable. Possibly, but it's mostly just a better system which works because railway lines are linear. On British railways at least (not sure about around the world), each signal informs the driver about the current state of the next two signals. - Red (danger): absolutely do not enter the next piece of track (with serious consequences if breached), - Single yellow (caution): the next signal is red, - Double yellow (preliminary caution): the next signal is a single yellow, - Green (clear): next signal is double yellow or green. This way you can tell if you are catching up with the red and adjust speed accordingly (and I guess they would incorporate knowledge about the line, ie. if they know there is only one signal to the next station they wouldn't worry too much about a double orange). I think the "smart motorway" variable speed limits are an attempt to implement this on the road. Unfortunately a large number of people think the temporary speed restrictions cause congestion and others think smart motorway simply means no hard shoulder. You can't really treat current traffic signals like railways signals, but motorists would do well to learn to regulate their speed better and understand the concept of average speed.