I can't help but I can tell you that just looking at Google maps I found a route that cut my time in half on a 60 mile rush hour trip yesterday. If I followed my navigation I would have hit traffic from start to finish but my way kept moving the whole time.
With results like that and some frustration with the voice command, I avoid relying on my navigation as much as possible.
If there is any chance of traffic, you are going to save time by not driving, finding your own route that avoids the worst spots and then start your trip with a good plan.
What I've been doing is starring addresses in Google maps on my smart phone. It gives me a good idea of relative locations and that is the key to finding efficient routes.