Main Roads. Noisy, Bright and vehicles travelling at speed, probably not the best conditions for a bird or magpie, let alone a person to live. In my findings in cycling around suburban streets and main roads, I get swooped countless times within only 1 suburban block whereas I can ride kilometres on a main road and no swoops or even a trace of a bird in sight.
Yes, you do have to breathe in some pollution (which is bad for your health, its a potential carcinogen, I dont like it myself) but if you do have to travel somewhere by bike or on foot, it is a tradeoff between breathing in the pollution (if that bothers you) and getting annoyingly swooped.
This is just what I found. Stay safe around magpies and try to limit breathing in pollution. -tman