Speed Signs Required In Both Directions?

When there is a change in the speed limit (say 50 to 60 one way and 60 to 50 the other way), does there need to be a posted speed sign in BOTH directions?

Thanks

bump ... Anybody have any ideas on this one?

I can not find anything specific about this.

Yes it does, from a signage standpoint. However, if you exited an 80 km/h zone into a 50 zone while going east, the lack of an 80 km/h westbound sign at the changeover point doesn't provide a defence to going 80 in a 50 zone, if that's what you're asking. They don't really expect drivers to look in their rearview mirror. So, it would be a valid defence if you were going from an 80 to a 50 zone and there was no 50 sign, but there was an 80 sign in the opposite direction.