This Truck Broke a Bridge With Its Wheels Up

This truck just broke through a bridge, with four of its wheels in the air. A loaded dump truck can weigh as much as fifteen cars. Put all that on too few tires, and each one presses down hard on the same small spot. So the law limits how much weight each axle can carry. When the truck is loaded, it drops its extra wheels and spreads the weight out. Empty, it lifts them back up to save its tires. This 3D animation shows why many dump trucks drive with some wheels in the air. A loaded quad-axle dump truck can weigh around 70,000 to 80,000 lb, about as much as fifteen average new cars. On too few axles, every tire presses that weight onto a small patch of road or bridge deck. On US Interstates, federal rules limit a single axle to 20,000 lb and a tandem to 34,000 lb, and the Federal Bridge Formula limits weight by the number and spacing of the axles so bridges aren't overloaded. States set their own limits on other roads. Lift axles, also called pusher axles, solve this. When the truck is loaded, air springs push them down so they carry part of the weight. When it's empty, air bags lift them to cut tire wear and fuel use. The truck, the bridge and the collapse in the film are made up and shown in slow motion; real bridges are built with safety margins. The weight arrows show relative axle loads, not measured values. #Shorts #Trucks #Engineering