Lightering (also called lighterage) is the process of transferring cargo between vessels of different sizes, usually between a barge and a bulker or oil tanker. Lightering is undertaken to reduce a vessel's draft in order to enter port facilities which cannot accept very large ocean-going vessels. Lightering can also refer to the use of a lighter barge for any form of short-distance transport, such as to bring railroad cars across a river. In addition, lightering can refer to the process of removing oil or other hazardous chemicals from a compromised vessel to another vessel to prevent oil from spilling into the surrounding waters.