I've noticed that sometimes the navi indicates that I'm on the freeway/highway parallel to the road I'm actually on. Most of the time this happens when I just got off the freeway/highway. It doesn't correct itself until I make a turn.

 

This is happens because sattelite tracking and maps are not very precise. Navi places the car icon on the nearest road to the position found by GPS. When two roads are close to each other- like a highway and an exit ramp- navi is getting confused. This is just a limitation of the technology