Street signs on highways

Place: North of Portland on I-5

Design issue: How many times have you been driving down the highway and wondered what the speed limit is, but couldn't see a sign? Or similarly when you see a sign coming up, but a big truck blocks it out as you drive by? This is both annoying to drivers and unsafe.

Possible solutions include: signs on both sides of the road; bigger signs that can be seen farther away; wireless transmission of upcoming sign content to a screen in your car that tells you the current speed limit and lets you review signs you've just passed; putting trucks in a seperate designated lane in the center of the road similar to a carpool lane where they don't obstruct vision to the side of the road. Any other ideas?