A quarter mile is a common distance used for horse racing, drag racing, and track and field sprints. It is now also the farthest distance at which U.S. Environmental Protection Agency (EPA) will consider two emission sources to be “adjacent” for purposes of major source air permitting. Under a new EPA final rule applicable to upstream and midstream emission sources in the oil and gas sector, new or modified equipment or activities are “adjacent” if they are on the same surface site or on sites that share equipment and are within one quarter mile of each other.