Me too, I've pretty much given up on biking anywhere within the city limit even though we have some bike trails and big parks. It's mainly because of the automobile exhaust, it just doesn't feel healthy which was the original intent.

Even way out in the country and in the National Parks (only 45 minutes by car) you find yourself either still on a (less traveled) road or on a trail that is more risky. You had better pay attention on the trails and not "space out" in any way. A fall becomes a bad accident as we get older.

A friend of ours uses a three wheel, recumbent bike which is great; it can be an active workout or a very laid-back experience (Stop, Look and Listen) but you always want nice, paved pathways whenever you can get them.