Mirror on crossing signal

[illinoistrains]

I came across this picture and it looks like the signal (crossbuck + stop sign) has a round mirror underneath. My guess is it's to improve visibility and an otherwise oddly angled road. Any thoughts?

http://railpictures.net/viewphoto.php?id=370538&nseq=7

[Smjh1979]

Maybe it's for a blind spot? We won't really know since we don't have a 360 degree view of the crossing.

[MD2020]

Thats there in case you are stupid and don't yield for the train so you can see your ass getting hit.

[SantaFebuff]

Yep, exactly. Those mirrors help drivers check the trains coming because they would be in the driver's blind spot at that angle.

Cheers,
Joshua