Each of the railtypes behave a bit differently and NUTS trains are trying to use that to make more differences between various train classes. While train stats are important, each railtype shares some way how it works.
NUTS also adds Universal rails (PURR). Since they are universal, any vehicle can drive on them - therefore you can autoreplace between any two railtypes easily. As another thing, there are 5 colour variations which offer the player various usages. For example you can mark important spots on the network, differentiate tracks with different purpose, or even control bonuses for MEOW train class.

Rail

As the basic starting railtype, the normal rail comes in two versions - electrified an unelectrified, but the difference between them is not really anyhow especially important for NUTS.
Much more important is the mechanic that rail uses the lowest curve length speeds of all railtypes.

Monorail

Monorail is something like a middle option which has +50% of curve speed in compare to normal rail, which makes occasional short curves viable on your network.

Maglev

As maglev has +100% speed in curves compared to rail, they can almost ignore any slowdowns in curves, making them effective in areas crowded with rails where you cannot afford longer curves.
It is also noteworthy that maglev does not use Tractive Effort.

Universal railtypes (PURR Universal Rainbow Rails)

  • The universal railtype creates a very handy tool for various occasions. The first most common usage is just for autoreplace purposes, to be able to replace between trains running on various rail types (e.g. rail X monorail) comfortably, quickly and automatically.
  • Second most interesting feature is that you can have different railtype trains running on the same diagonal tile, no to mention that it can also be used to mix various trains on the same network, regardless which is their "home" rail type.
  • The curve speed used is always decided by the engine and it's "home" railtype.
  • There are 5 colours: CLEAN, RED, YELLOW, BLUE, GREEN PURR, they only differ in visual appearance unless you use MEOW train class.
  • It is a lot more expensive to construct than any other rail.

WETRails

Since playing with ships has many downsides (like ships being dumb), time has come for ship/train revolution!
  • WETRail uses same curve speeds as Rail
  • WETRail has it's own signals.
  • WETRail has animals too!