Normative Signs: The Poetry of "Ought"

This one is in Washington, DC. (That’s the Capitol in the background.)

Exactly what’s being demanded here seems to depend on how you parse the sentence. Is it “You must [push the call button and thereby call for walk signal] before daring to cross the street”, or is it merely “You must push the call button IF you want the walk signal”?

Thanks to Wayne for sending this.