6. NASA Crawler-Transporter
World’s biggest what? Self-powered tracked vehicle.
Built by: Marion Power Shovel of America.
There are two crawler-transporters used by NASA, and today they carry space shuttles — boosters and all — along with each shuttle’s Mobile Launcher Platform into position. While not as large as the Bagger 288 above, the crawlers are the largest self-powered vehicles in the world, and can manage two miles per hour (compared to the Bagger’s 30-some feet a minute) when unloaded.