How do train wheels not skid or lose traction?

Question

Basically the title. Considering that train wheels are made of metals and run on metal tracks, how do they prevent wheelslip or loss of traction especially when starting with heavy loads or when going uphill? I’ve heard of sandboxes which can be used to provide more grip by spraying sand onto the track but I’m not sure if they’re still prevalent.

Thanks!

In: 72

Answer 1

There’s two kinds of friction: traction/grip (good) and rolling resistance (bad). Steel wheels on steel tracks won’t provide as much traction as rubber on asphalt, but they’re still good enough to gradually accelerate/decelerate trains. The rolling resistance is far, far less, which is why trains are so energy efficient.