Why Do Semi Trucks Have 18 Wheels?

No matter where you go on the road, a huge truck will eventually roll past you with a clap of thunder. Whether it’s hauling electronics bound for the big box store, a fuel for the next truck stop, or vegetables enroute to a large distribution center, these rigs are some of the most important cogs in the industrial machine. Trains and planes may handle the most urgent delivery, but large trucks perform the daily grunt function and consider the final part of a complicated distribution network.

Therefore, how did 18 wheels turn into a standard for semi trucks? One phrase: containerization.

Decades before 18 ­wheelers were blowing by on the method to Walmart, cargo was shipped all over the world seeing that break bulk. Rather than everything positioned within an individual container, break mass shipping intended cargo will be loaded onto a boat or truck separately. The shipping technique was tiresome and labor­ intensive, and whenever a ship would prevent on its path, every item will be shifted around to support even more cargo. Finally, off­loaded cargo will be kept in a warehouse before trucks found bring those items to their last destination. It had been not really the most effective means by any measure.

Inklings of a different technique ­­containerization ­­appeared as soon as the late 18th hundred years in the kind of coal-­ferrying English container boats and wagon trains. Essentially, shipping and delivery businesses designed big boxes which can be stuffed, stacked on a huge ocean­ heading ship, and off loaded. From there, the boxes could be put straight onto the trunk of a vehicle and driven to its last destination.

The International Firm for Standardization developed containerization standards between 1968 and 1970, that regulated the size, weight, and the typical concentrating on container lengths. Five had been chosen, and of those, most containers are either 20­ feet or 40 ­ feet long, with the average 40-­ foot container capable of carrying up to 60, 000 pounds of cargo inside.

However , carrying heavy loads is usually taxing on pavement. The U. S. Department of Transportation generally restricts weight limits to 80, 000 lbs for gross weight, 12, 000 lbs for the steering axle, 20, 000 lbs per single axle, and 34, 000 lbs per tandem unit. To be able to move those containers to and fro over land, more wheels and axles are needed in order to comply with the regulations. That meant 60, 000-pound trailers needed at least three axles and 12 tires. Heavier trucks required a third axle on the back for the trailer, and trailers gained a second axle of four wheels. All told, there are four axles with four wheels on each axle, and one axle-the steering axle-with two wheels on it, for a total of 18 wheels.

A coalition of trucking and shipping firms have pressed Congress to let states raise the weight limit for trucks to 91, 000 lbs. on six axles, from 80, 000 on five today, as a way to reduce costs and move more freight. Trucking firms contend as long as the extra weight is spread out, it will cause no additional road damage-and make 22 wheels, rather than 18, the new standard.