this work is done over time which reduces the deceleration (negative acceleration) applied to the vehicle occupants. A smaller amount of energy is consumed in the work of crumpling the plastic containers. In cold climates, water-filled attenuators are either avoided, or have additives such as magnesium chloride salt added to them to prevent freezing. Fitch barriers A Fitch barrier consists of sand-filled plastic barrels, usually yellow-colored with a black lid. The "Fitch Highway Barrier System" was invented by race car driver John Fitch after the 1955 24 Hours of Le Mans race when his co-driver, Pierre Levegh rear-ended Austin-Healey driver Lance Macklin at high speed, launching his car through the air and into the spectator's area. The car burst into flames and took the lives of Pierre and 84 spectators in one of the worst accidents in racing history. He stated he was inspired by sand-filled fuel cans which he used to protect his tent from strafing during World War II. Early prototypes were self funded and tested due to low initial support. As a proof of concept Fitch used liquor barrels filled with sand to create the necessary impact attenuation, then personally crashed reinforced vehicles into them while recording with a high speed camera to capture the rate of deceleration. Fitch barriers are often found in a triangular arrangement at the end of a guard rail between a highway and an exit lane (the area known as the gore), along the most probable line of impact. The barriers in front contain the least sand, with each successive barrel containing more, so that when a vehicle collides with the barrels they shatter, the kinetic energy is dissipated by scattering the sand, and the vehicle decelerates smoothly instead of violently striking a solid obstruction, reducing the risk of injury to the occupants. Fitch barriers are widely popular due to their effectiveness, low cost, and ease of setup and repair or replacement. Since first being used in the late 1960s, it is estimated that they have saved as many as 17,000 lives and approximately $400 million per year in property damage and medical expenses. Non-gating Non-gating impact attenuators arrest the motion of vehicles that impact head-on, whilst deflecting vehicles that impact the side of the barrier. They are anchored and more expensive, but can be used in tighter spaces. Crash cushions Crash cushions are constructed of multiple segments, which crumple into each