An arrestor bed, also known as an engineered materials arrestor system (EMAS) or arrester bed, is a bed of engineered materials built at the end of a runway to reduce the severity of the consequences of a runway excursion. It is an area of special material designed to stop a runaway vehicle, such as a landing aircraft or a semitrailer, that is out of control. Arrestor beds are designed to assist heavy vehicles if they lose control, and they include gravel arrester beds, runaway lanes, and speed control lanes. The first EMAS was developed in the mid-1990s by ESCO/Engineered Arresting Systems Corp. (later Zodiac Arresting Systems) as part of a collaboration and technical acceptance by the FAA. The fourth generation EMAS arrestor beds are composed of blocks of lightweight, crushable cellular concrete material, encased in jet blast resistant protection, designed to safely stop airplanes that overshoot runways. Arrestor beds have been installed at airports where the runway safety areas are below standards, and their ability to stop aircraft with minimal or no damage to the airframe and its occupants has proven to bring results far beyond the cost of installations.