Freight train speed question

I'm not sure which forum this question belongs in but: Why are freight trains limited to 50mph? Most track in the US is Class 4, shouldn't it be good for speeds up to 60mph for freight? Or is it due to braking issues?

For freight trains on Class 4 and Class 5 track, a railroad may reduce the speed limit for downhill movements (to prevent runaways) or, where that is not an issue, to reduce fuel consumption per ton-mile. I think that since generally the downhill limit is going to be less than 50 MPH where safety is a concern, it's almost always fuel costs that's driving this.

RandallW wrote: ↑Mon Oct 16, 2023 4:16 am For freight trains on Class 4 and Class 5 track, a railroad may reduce the speed limit for downhill movements (to prevent runaways) or, where that is not an issue, to reduce fuel consumption per ton-mile. I think that since generally the downhill limit is going to be less than 50 MPH where safety is a concern, it's almost always fuel costs that's driving this.

Reducing speed for the railroad companies, is like slow-steaming to the companies that operate the big containerships.
You want cheaper rates, your cargo will get there when it gets there.