It's a common belief in the U.S. Army that troops marching in step across a bridge can set up a resonance which can cause the bridge to collapse. This is the ostensible reason for the command, "Route step, March", in which the troops stay in formation but not in step. Is there any basis for this belief?

They tested this, and they could not get their bridge to collapse.

As much as I love and respect Adam, it is my opinion that his machine he built, with all the feet did not accurately reproduce the phased force of soldiers marching in step. I think an oscillator more along the lines of Tesla's earthquake machine would be a better simulator of marching soldiers.

I am in a high school marching band and we were at a parade one day marching accross a bridge. Now of course we were all in step and half of us could feel the bridge bouncing up and down. Could our marching band somehow make the bridge collapse?

I feel that the bridge march was not accurately simulated. Mythbusters did not take into consideration any wind speed around the bridge. Usually there is an up wind coming off the water underneath the bridge. The road needs to be two lanes wide due to the fact that on coming cars are approaching from the opposite direction. As the soldiers come on to the bridge the weight distribution changes as soldiers move forward.
This myth needs to be revisited.

Actually yes, this one was done wrong, but not for the reason of wind.

The problem is that the method they used beat the crap out of the bridge and didn't take into consideration the natural resonant frequency of the bridge itself. Basically, you have to "tickle it" and not "punch it to death".

The key to doing this one right is to realize that people marching lockstep is at a far, far lower frequency, much closer to the natural resonance of a real bridge. The miniature bridge used on the show had a much higher frequency required, so neither mechanism they used would ever have done anything but go over the weight limit on each step

What I would probably do is to build another bridge, then use a variable "vibrator" to find out where the bridge resonated at. You should be able to feel it with your bare hands because it will be the frequency that makes your hand buzz like crazy when you touch it -- the bridge will resonate and pass much more of the original energy into your hand. Once that frequency is found, make a much bigger one that vibrates at the same frequency (or at an even harmonic of it, be it 1/2 or 2 times the frequency if they like) but puts more power into it. It *will* shake apart given enough energy!

They'll have to make sure that they don't weld it like the one on the show before, too. The welds on a real bridge are far weaker than the ones on the show because the welded area is much smaller in proportion to the size of the bridge. Making the miniature means having to miniaturize everything.

Stomp stomp stomp only works on real bridges. There was a millennium special about the foot bridge constructed across the thames for the 12/31/2000 celebration. The foot bridges there DID resonate, but didn't fall apart because of shock absorbers at either end of the bridge.

"Route step" is nothing more than a relaxed way to move a formation of troops. The formation loosens up and individuals only maintain a sort of basic position. The primary difference between "route step" and a bunch of men walking along is the perception that they are in a formation and still need to be attentive to commands.