Before he suddenly left us, Harry Kline had approached me with the by-pass for El Paso. It is now published as an article here on RTA, El Paso By-Pass. We had briefly discussed, via Private Message, the idea of starting a thread about city by-passes such as this one. I had told him, if he started the thread, I would gladly contribute to it. Now he's gone, so I'm going to start this one in his honor.
Most of the time, when on an interstate, taking the "belt-loop" provided by the Highway Commission is the normal way. These are the loops where another number (or two) is added. An example would be 805, a belt loop around San Diego for I-5. Or, perhaps, I-210 in LA, which is a belt loop around LA instead of I-10.
Our favorite by-pass, one we often use when traveling on I-70, concerns St Louis when traveling east/west. Downtown St Louis is something we try to avoid unless we have to be there. We also want to try to avoid the traffic around Lambert Field (STL) and St Charles, and these days, other certain areas. So, here's how we do it:
EASTBOUND: Leave I-70 at exit 224, MO-370 East. Take that until it ends at I-270 eastbound. Continue on I-270 east. You will cross the Mississippi River on a new bridge, but if you look to the south (your right) you can see the old Chain-of-Rocks Bridge running more-or-less parallel to the new bridge. (I say more-or-less, because the old bridge actually has a *turn* in it.) Once in Illinois, I-70/I-270 join together.
WESTBOUND: Watch the signs on I-70 as you approach St Louis. Follow the I-270 signs - very easy, smooth, seam-free. As you cross the Mississippi River on the new bridge, the old Chain-of-Rocks will be to the south (your left), but not as easy to see as from the eastbound side. You'll be on the 270 for about 20-some miles before you see the exit to MO-370 west, which is either exit 21 or 22. Then take that until you find yourself with a choice of I-70 west or east.