system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do trains not slip when it's raining or when going uphill?
gpt
I used to drive a train for a number of years. Trains have compressed air powered sand dispensers that drop sand onto the track just in front of the drive wheels. The crushed sand provides grip on steep / wet / slippery rail lines.

The downside is the onboard sand reservoirs deplete quite quickly so you have to use them a little sparingly.

Cheers.