inherent movement of air under the vehicle. I believe at any normal driving speed this movement would dissipate any downward force the birds produced over such a large area of bridge, distinct from the truck's wheelbase's influence, that we could assume the birds weighed virtually nothing. In conclusion, unless the truck had an airtight container, or was stationary with very little gap between the floor of the cage and the road (to allow transfer of force directly downward), then I feel the truck would be likely to make it. Thankyou anonymous (2 posts above) for pointing out the airtight container issue! It took a while!! On the other hand if the cargo were kangaroos and the roos were able to launch before the truck got on the bridge and land after the truck crossed to the other side, then the weight of the roos would be moot since the weight would be timeshifted to pre and post crossing. But wait! These are pidgeons - can they be trained to fly back to the truck? If so, the driver releases them before crossing, drives across then calls the pidgeons back to the truck and cages them again. Only the 4950 truck+driver rests on the bridge and he is able to safely cross. It does rely on having well trained and well-behaved pidgeons, but they can be trained to home in on a known place. It would also be preferable if the pidgeons didn't fly low directly above the bridge as they