Resonance frequency??

Of late, whenever I get stuck in a traffic jam right on top of a fly-over, yes, right on top of a flyover, from where the only means of escape is a ejection seat with a parachute, I have felt like I am sitting on one of the forks of a tuning fork.

At the beginning, I thought that it was the wind at that altitude (yeah, as if we are talking of 15000 ft above mean sea level). No, there was no wind. I thought, it was due to fast moving traffic in the opposite direction. No. It happened even when there was no traffic. That was when I thought about the concept of resonance. With most vehicles idling (not to be mistaken with making idlies) and the rpm being close to 1000rpm, could it be possible that the flyover's natural frequency is close to it? Which means, when enough numbr of vehicles start idling on the flyover, the flyover would start moving rather violently!

Hope someone somewhere who is supposed to read this post reads it and checks the natural frequency of the flyover over Diary circle....

~Sid