Hopefully, your wife would be literate enough to read the document and determine that it is NOT incriminating, merely an agreement to appear in court. See, Court is where you argue these things, not the side of the road. If you and your wife don't understand that then you might well have something bad happen to either you or your wife.
I dont forcibly have to agree to appear - that is my prerogative and I will face the legal consequences if thats the course of action (decidedly stupid) I decide to take.
My point is - you can not be forced to sign anything
and I will for the umpteenth time ask why ticket cams are exempt from this signatory promise to appear?