Questions about the LIRR

How is this actually pronounced? Lar? Is it really used?

I’ve only heard it as the letters pronunciation L.I.R.R. or L.I double R. Or perhaps I heard it Lrrrrrrr but since I don’t know how that is pronounced I’m not sure.

My daughter pronounces it ‘lirr’ as a word, not as letters. She likes to watch me cringe when I hear it.

I taught her well.