This is more of suggestion than extension request.
It would be practical to be able to set some kind of control on construction cost for terraforming in water.
Such as filling water depth with slope, raising terrain of deep water, fill lake and building tunnel underwater.
This would allow making crossing water body using terraforming cost prohibitive and enforce building of
bridge(which cost maintenance) or tunnel. Also, game wise more consistent.
Similar happens in dry land too. It is almost always better to blow up hills or mountains or valleys instead of building bridges or tunnels since the former is a one-time payment, while the latter implies construction but also maintenance costs, which are forever.
QuoteIt is almost always better to blow up hills or mountains or valleys instead of building bridges or tunnels since the former is a one-time payment, while the latter implies construction but also maintenance costs, which are forever.
This is a fine line - the main thing is that there shouldn't really be a benefit to either over adapting the route to suit the landscape. This is the art of balancing paksets....
For what it's worth I think that for anything over 1 or 2 heights (depending on whether it's a half or double height pak) the 25 (or so) year costs should be more to make earthworks than it does build bridges or tunnels. The percentage of bridges/tunnels compared to total way length should also be quite low, certainly less than 10% for lines which have a relatively sparse service. Lines that are entirely elevated or underground should only be viable if they are metro lines (i.e. running at full capacity with services that are also full).
As a rough guide, assuming that maintenance per month is 1% of build costs, I think that bridges/tunnels should have around 10x build and maintenance of plain ways, and that point terraforming in a half height pakset should be 1.5x tunnel/bridge build cost, and tile terraforming 4x tunnel/bridge build cost. Now, obviously terraforming cost is fixed over time whereas way, tunnel and bridge costs will probably slowly increase as speeds get faster, this alters the above balance, in earlier years favouring high and long bridges, and in later years favouring extensive earthworks. Given this is might actually be better to set the terraforming cost dynamically based on available bridges and tunnels (extension request?)
If capital is large, maintenance less option is always better as long as cost is well, reasonable.
Just remarked the fact that there is no cost penalty on working around the water. I definitely think working around water costs more than on dry land.