Colin,
thank you very much for your response. It might be better in future to discuss issues with performance on
this thread to keep them all together for ease of reference: poor performance is not a "bug" as such. I should be very grateful if you could head over to
this thread and answer the same questions as I have asked Dante so that I can get an accurate idea of how to calibrate and assess the performance.
I am still not sure what to make of the issue with city resizing: I have not been able to reproduce it, and it does not relate to any code that I have changed in making Simutrans-Experimental. It might well be that this is a rare and intermittent bug from Simutrans-Standard. Especially since you have resolved your issue, I do not plan to take that issue any further at this stage, but it is useful to be aware of it.
Finally, on the subject of steam, steam railway locomotives have, in effect, a lower power output at lower speeds, as described
here. That caused them to be slow to accelerate compared with diesel or electric locomotives of similar overall power, and also to be poorer at climbing gradients. This had a substantial impact on the history of railways, firstly in that railways in the days of steam were built taking more strenuous efforts to avoid gradients than would be prudent if diesel or electric traction was used (leading, for example, to less straight routes than would be desirable in modern times with faster, more powerful trains), and also was an important factor in the demise of steam (and it is no coincidence that steam was first replaced on local stopping trains where the improved acceleration of diesel or electric traction could make the most difference). To simulate that, I have also given steam powered vehicles in Simutrans-Experimental lower power at lower speeds: they will therefore give less than their rated power until they reach a certain speed. However, I am wondering whether this ought be restricted to steam
railway vehicles, as the physics are a little different for steam road vehicles (which were inevitably driven through gears, rather than directly as with steam railway locomotives) and steam ships (which would drive a propeller or paddle which would turn freely in the water, the speed of the propeller or paddle shaft not having a fixed relationship with the speed of the boat itself). Your (and anyone else's) thoughts on that issue would be appreciated indeed.