Lightning striking a bridge while someone is on it?

Lightning sometimes flows from the ground to the sky and sometimes from the sky to the ground. In lightning that strikes tall ground-based objects, it's almost always ground to sky.

Electricity flows through the path of least resistance from the ground to the sky. Air has high resistance. Metal has low resistance. A human body is in between the two in terms of resistance. If you have a tall metal structure, the lightning will flow most easily through that metal as far as it can, and through air the rest of the way. If you are on the side of the metal, the electricity will flow through the metal, not through you. You'll be like a bird on a power line. If you are standing on top of the metal, then the electricity will flow through the metal, and when it reaches the end of the metal, the electricity will flow more through you than through the air around you because you have lower resistance than air does. That would fry you.

So, don't climb to the top of the bridge during a storm, but you'll be completely fine otherwise.

Other than getting very wet.

In case someone points out that bridges are painted: the paint is thin an provides very little resistance compared to a human body, so high-voltage electricity will flow through metal and then paint rather than through you.

Lightning behaves in a very strange way. It is DC but because of it's very short duration, you have to use high frequency AC theory to predict how the current will pass through a conductor. As for the steel bridge, provided that you are a safe distance away from the strike not to be affected by the heat, and far enough away not to be in the 'Side Strike' range of the bolt, you should be OK. It will be a different story for your mobile phone, the EMP from the strike will kill the electronics.

I think you'll be fine. The bridge is well grounded and made of metal. But it's conceivable that if there are any breaks in the metal, like with rubber or concrete, that a voltage could be developed across those breaks that could be dangerous. And if one was standing across one of those breaks that they could get zapped.

Also, if the bridge isn't grounded...ever notice you see birds sitting on distribution lines but never on high-voltage transmission lines? That's because the birds body gets charged up right along with the wire voltage, up to 18KV(peak voltage for a normal three phase distribution line) and down to -18KV, 60 times a second. The current required to do this, which flows through the bird's body, is not bothersome. But now go to 500KV(typical peak voltage for a 345KV transmission line) and the current is enough to bother the bird. The bird's body is not completing any circuit per se, which is why the 13KV line isn't vaporizing the bird in a matter of milliseconds. But there is small amount of charging current.

So if the bridge(or the particular section of the bridge one is standing on) isn't well grounded, one could still feel something.

Coffee break time. Lightning is weird. It does unpredictable things. No one can tell you all about it.

Clear the bridge and get under it or into a vehicle with rubber tires until the storm passes.

The bridge is grounded. This is the part to inspect first, The grounding.

If you were on or near a current conducting part of the metal bridge and even if 0 current flowed through your body you would still get burned from the intense heat generated by the high current through the low but finite resistance [(I^2)*(R)] of the metal.

Of course if your body is part of the lighting's conduction path then you would suffer both heat and shock damage in addition to being frightened out of your underwear.

depends how close to the lightning strike

if you are close you can be killed by the voltage field created around the conductor

(cows have been killed by lightening striking a tree (not the cows)

the lightning created a voltage drop in the ground decreasing the further you got from the tree. The voltage drop between head and tail of the cow was enough to kill them

I think you'd be okay. It could act like a faraday cage and protect you. Another reason is it seems something like that would've made the news at some point. I never heard of it happening.

Generally, you will feel a slight tingle or none, as there are numerous parallel paths with much lower impedance than your body. The thunder however has potential to cause hearing loss.

Why don't you climb up one next thunderstorm and be a guinea pig? The worst thing that could happen would be electrocution. However, that would be the best thing for everyone else.

NEVER HAPPEN, BRIDGE IS MADE OF METAL AND SITS IN WATER GROUND,ITSELF ACTS LIKE A THUNDER RODE. PEOPLE WORK OR WALKING IN BRIDGE LIKE THEY ARE SEALED INSIDE A METAL CASE .