Another thing. Pre-rail-passenger transport, the game seems to generate an inordinately large number of passengers.
I mean, if I in 1800 start up a stagecoach network between 15-20 small towns, 8 passengers per stagecoach, doing 10km/h.
In real life, the "flying coach" between Oxford and London took an entire day to do that journey from about the 1680s until the coming of the railways, and there was ONE coach each way daily. So 8 passengers in each direction, or thereabouts.
In simutrans, I'm having to depart stagecoaches as though they were minicabs, back to back, I have congestion on my roads!
I presume the game uses the same mechanism to calculate passenger numbers across the whole time period. In reality, the availability of transport at a given area drives demand, along with the wealth/social group who want/need to travel. Until the coming of the railways made the country 'smaller' the demand was fairly limited.
I don't know whether the passenger generating mechanism can just be tweaked to be minimised until the opening of the Liverpool & Manchester railway, say, or if there's a smarter way to do it (based on whether a town has a rail station in it's vicinity say).