DIN  Suggested by claudeserieux 

Alleluia

PS. I'd already seen this signboard when I was on holiday in Canada, but didn't understand who should move the first...

First In, First Out

Ok thank you

But it's somewhat difficult to guess who was the first in, if we didn't look at it before, when we just focus on a strange signboard like that with everyone with a STOP at the 4 intersections!