A car crusher is an industrial device used to reduce the dimensions of derelict (depreciated) cars prior to transport for recycling.
Historically, because scrap cars were too big and bulky to transport to the sites that turned them into reusable material, and the cost to transport them was uneconomical because, at times, it would cost more to send it than the car was worth, because transportation costs were determined by weight. Since uncrushed cars were less dense and took up more space, even for a short haul, the scrap cars were worth less than it cost to deliver them.
Cars can be crushed either dropping heavy weights onto them, using an excavator bucket or mechanical grab, but these rudimentary means can be time consuming and produces inconsistent scrap sizes. By contrast, having a dedicated car crushing machine speeds up the compacting process and results in more uniform scrap bundles.