840 is a bypass around Nashville 140 to I40. Its about 17 miles further than thru Nashville, and usually about two hours or more faster. It is good 4-lane, with very little traffic. The truck traffic is getting heaver on 840, as many thru trucks find it is much faster for them, although a bit further. To me, it does seem to be a lot longer, until I was told what it measured. Some truckers have told me that they save fuel by taking the longer route instead of all the start-stop through downtown.