Trains where originally designed to keep the train on track. At the time trains where pulled by horses and used to transport coal (and such) out of mines. The two functions have very different requirements:
- Keep the train on track
- Push the train forward
How effective would a solution be to push/pull the train forward that pulls on a serrated track?
Or some other surface that provides far more grip/traction?

  • $\begingroup$ Funicular trains use some type of gear or cog for propulsion. I suggest that the simplicity and cost of a single set of tracks is the driver for current general usage. $\endgroup$ – Tiger Guy Apr 26 '20 at 0:31
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    $\begingroup$ @TigerGuy No, funicular uses a rope for propulsion, and rack railways use the rack for propulsion. In both cases the wheels are here only for staying on the tracks. Although mixed rack/normal trains exist as well where whells also do propulsion. $\endgroup$ – Bregalad May 21 '20 at 22:24

Trains do sometimes use different means for propulsion: Rack railways use cogs, and Funiculars use ropes

I think the reason these are uncommon is that the available traction of smooth tracks is more than sufficient for all but really steep slopes (>10% ). Train engines may be limited in both torque and power when it comes to moving a heavy train up a steep slope, so the lack of traction is only part of the problem. That's why trains tend to avoid slopes, or if absolutely necessary go up in S curves or zigzags.

Racks have hugely greater maintenance costs, and hugely greater friction resistance, so they would be avoided except for special circumstances (very steep slope, very slow speed, and special engine/light load).

Even in mines, I think it is more common to use a combination of smooth tracks and elevators - it's worth dumping ore from one to the other rather than laying down rack rails.


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