And then there's
Angola, which in terms of facilities shared by both directions of traffic, I think is better than the other examples mentioned so far for several reasons:
1. Ramps are on the right so traffic doesn't have to enter/exit from the left lane
2. Doesn't require a massively wide median since parking isn't in the median
3. You get to walk over the highway in a covered bridge, which is pretty cool
4. For toll roads, it can't be used to U-turn since the bridges are pedestrian-only
So yeah, all of that is basically a long way of saying Angola is one of the best service areas there is.