It'll also route you around major delays if it can. This saved me a three hour tailback only weeks ago (arriving at work after lunch would have been...irritating) and literally last week I didn't bother to set it on the way home and ended up in 30 minutes of standing traffic that it would have told me to avoid (there's an alternate route that's 10 minutes slower, but once you're in the wrong road you're committed and can't go back).