Oversized luggage is luggage that does not fit within the maximum allowable dimensions set forth by a transportation provider. The term most often refers to baggage checked for air travel, but can also apply to air travel carry-on bags and to luggage transported by bus, train, or ship. Some transportation providers strictly forbid passengers to carry oversized luggage, while others will allow it upon payment of an additional fee.
At one time, baggage size restrictions were almost universal, at least for air travel. Over time, that has become less so. While common standards do exist, each airline sets its own policies as to what constitutes oversized luggage and sets policies and fees regarding the ability of customers to check or carry such bags.
Airlines might also have different restrictions based on geography and on specific flights. The maximum allowable dimensions and oversized luggage fees may be different in one country than in another as well. Such luggage could be banned entirely on some flights and merely incur an additional fee on others.
In air travel, the maximum allowable dimensions on luggage are usually determined by the size of the aircraft. This is especially true of carry-on luggage, as the size of overhead bins can vary dramatically based on the model of the aircraft. In some cases, restrictions might also be based on local policies and governmental restrictions.
Baggage size restrictions also vary significantly for ground and sea transporters, such as trains and cruise ships. As with airlines, these companies typically base restrictions around the size of the equipment in which passengers ride. Like airlines, such companies might disallow oversized luggage or assess a baggage fee.
The designation "oversized" typically refers to the actual outer dimension of the luggage rather than its weight. Bags that weigh more than the maximum allowable weight are generally designated "overweight." The outside dimensions are often determined by measuring the bag’s length, width, and depth and adding those three numbers together. Carriers might also stipulate that no one side be longer than a specified length.
Airports and train depots often provide displays that contain a frame or box into which carry-on bags must fit in order to be allowed. This gives passengers an easy way to see if their items are within the required dimensions. Luggage that does not fit usually must be checked. While luggage typically refers to suitcases, trunks and other such travel-specific bags, cases, or equipment can be considered "luggage" and be subject to size restrictions. This includes musical equipment, strollers, wheelchairs, and anything else that is checked or carried on.