I've heard of stories where 'oh, we were doing physics on that but it was too much for the CPU so we disabled it' problem I have with that is that not all CPUs are equal, and it should be up to the player, not to DTG, as to what has physics and what does not. (Also, one of my common motifs of game design is OPTIONS OPTIONS OPTIONS! so I may be biased) I think individual options for things like hose physics, suspension and wobble, coupler slack, level of physics on AI trains (would be needed for hump yard work-can't turn off physics when disconnecting a car in motion on the hump) maybe even to the extremes of precise airbrakes vs simple airbrakes (though right now they certainly do not feel precise with the way the pressure bounces around). Those kinds of options could reduce a lot of the load that "extra" physics stuff that does not control how the train drives but still suck up CPU in order to let people with poorer CPUs still play at a reasonable framerate without much of a difference to usual (mostly just graphical TBH). Conversely, someone with gobs of CPU power could turn on more physics than usual or make the existing physics use more precise calculations in order to take advantage of the CPU they have.