has been selected and edited by New Scientist staff The practical engineer's answer is yes, of course the driver could cross! The surplus weight of 50 kilograms translates to a 1 per cent excess over the bridge's specified load maximum. An additional impulse force due to the truck bumping over a small stone in the road would be much greater than this 1 per cent, and any civil engineer who designs a structure of any sort with a safety margin anywhere near as small as 1 per cent deserves all the professional liability lawsuits he or she gets. the answer is no. Simply because the truck itself weighs 4950 KG right? And he scares away his 100 KG load that puts him over the limit. But unless the driver weighs under 50 KG which is highly unlikely or is strong enough to pull his truck over from the other side... then i guess it could work. It's funny that people came up with rediculous scientific answers when the answer is simple and answered by a 16 year old high school student. The truck wouldn't make it. Not for all the reasons of everyone elses posts. They are all plausible and most likely right if the scenario was put to practice, but i have a simpler answer and i am merely 16 in high school. Presuming the pigeons all took flight BEFORE the truck went over the bridge, assuming the truck weighs 4950, the truck drivers weight would be the cause