A retarder is a device used to augment or replace some of the functions of primary friction-based braking systems, usually on heavy vehicles. Retarders serve to slow vehicles, or maintain a steady speed while traveling down a hill, and help prevent the vehicle from "running away" by accelerating down the hill. They are not usually capable of bringing vehicles to a standstill, as their effectiveness diminishes as vehicle speed lowers. They are usually used as an additional "assistance" to slow vehicles, with the final braking done by a conventional friction braking system. As the friction brake will be used less, particularly at higher speeds, their service life is increased, and since in those vehicles the brakes are air-actuated helps to conserve air pressure too.
Friction-based braking systems are susceptible to "brake fade" when used extensively for continuous periods, which can be dangerous if braking performance drops below what is required to stop the vehicle – for instance if a truck or bus is descending a long decline. For this reason, such heavy vehicles are frequently fitted with a supplementary system that is not friction-based.
Retarders are not restricted to road motor vehicles, but may also be used in railway systems. The British prototype Advanced Passenger Train (APT) used hydraulic retarders to allow the high-speed train to stop in the same distance as standard lower speed trains, as a pure friction-based system was not viable.
Friction-based braking systems are susceptible to "brake fade" when used extensively for continuous periods, which can be dangerous if braking performance drops below what is required to stop the vehicle – for instance if a truck or bus is descending a long decline. For this reason, such heavy vehicles are frequently fitted with a supplementary system that is not friction-based.
Retarders are not restricted to road motor vehicles, but may also be used in railway systems. The British prototype Advanced Passenger Train (APT) used hydraulic retarders to allow the high-speed train to stop in the same distance as standard lower speed trains, as a pure friction-based system was not viable.
by Huvudpersson July 24, 2017
Get the Retardermug. by Grandepapa November 7, 2022
Get the Retardmug. 
Someone who stigmatizes and misunderstands physcology, the real world and other races, cultures in today's world. And is based entirely on misconception and misinformation.
by A700 March 10, 2022
Get the Fucking retardmug. Retard is a word middle and high schoolers use everyday to insult each other while online people say it’s a slur ☠️ so common to use it in nyc and philly
“he’s a fucking retard”
by philly goat January 28, 2023
Get the retardmug. by datboii.ya01 March 9, 2018
Get the Retardedmug. The over-use of certain mind altering substances. After which person(s) feel less mentally capable.
Also used in place of "over amping"
Substance abuse.
Also used in place of "over amping"
Substance abuse.
by Doping March 7, 2023
Get the Get retardedmug.