W/MX signpost meaning?

Model Railroader Prototype information for the modeler
1

I’ve seen a W over MX signpost around here. What does this mean?

Thanks,

KL

2

The sign tells the engineer to Whistle for Multiple Crossings.

3

Inneresting. I knew the W was for Whistle, but did not know the rest.

4

Thanks, Joe

KL