Cruise control

From Academic Kids

Cruise control (also known as speed control) is a system to automatically control the speed of an automobile. The driver sets the speed and the system will take over the throttle of the car to maintain the same speed.



Speed control with a centrifugal governor was used in automobiles as early as the 1910s, notably by Peerless. Peerless advertized that their system would "maintain speed whether up hill or down." The technology was invented by James Watt and Matthew Boulton in 1788 for use in locomotives. It uses centrifugal force to maintain a constant throttle position.

Modern cruise control was invented in 1945 by the blind inventor and mechanical engineer Ralph Teetor. His idea was born out of the frustration of riding in a car driven by his lawyer, who kept speeding up and slowing down as he talked. The first car with Teetor's system was the Chrysler Corporation Imperial in 1958. This system estimates ground speed based on driveshaft rotations and uses a solenoid to vary throttle position as needed.

Theory of operation

In modern designs, the cruise control may or may not need to be turned on before use — in some designs it is always "on" but not always enabled, others have a separate "on/off" switch, while still others just have an "on" switch that must be pressed after the vehicle has been started. Most designs have buttons for "set", "resume", "accelerate", and "coast" functions. Some also have a "cancel" button. The system is operated with controls easily within the driver's reach, usually with two or more buttons on the steering wheel or with a control stalk.

The driver must bring the car up to speed manually and use a button to set the cruise control to the current speed. Most systems do not allow the use of the cruise control below a certain speed (normally 35 mph/55 km/h) to discourage use in city driving. The car will maintain that speed by pulling the throttle cable with a solenoid. Most systems can be turned off both explicitly and automatically, when the driver hits the brake or clutch. Cruise control often includes a resume feature to resume the set speed after braking and a coast feature to reset the speed lower without braking. When the cruise control is in effect, the throttle can still be used to accelerate the car, but once it is released the car will then slow down until it reaches the previously set speed.

Advantages and disadvantages

Cruise control has many advantages but also some serious vices.

Some of those advantages include:

  • Its usefulness for long drives across sparsely populated roads. This usually results in better fuel efficiency.
  • It is also known in some places as the "poor man's radar detector", since by using cruise control, a driver who otherwise tends to unconsciously increase speed over the course of a highway journey may avoid a speeding ticket.

However, cruise control can also lead to accidents due to several factors, such as:

  • The lack of need to maintain constant pedal pressure, which can help lead to accidents caused by highway hypnosis or incapacitated drivers; future systems may include a penalty switch to avoid this.
  • When used during inclement weather or while driving on wet or snow- and/or ice-covered roads, the vehicle could go into a skid. Stepping on the brake – such as to disengage the cruise control – often results in the driver losing control of the vehicle.

Many countries establish that it is illegal to drive within city limits with the cruise control feature activated.

Adaptive cruise control

Some modern vehicles have adaptive cruise control systems. These use either a radar or laser setup to allow the vehicle to slow when approaching another vehicle and accelerate again to the preset speed when traffic allows. Mercedes-Benz was the first to offer such a system, under the Distronic name, but a similar adaptive system is now offered by Lexus.

Current implementations

Volkswagen will introduce the technology to the mainstream with their 2006 Passat. Other vehicles with adaptive cruise control include the Audi A8, BMW 5 Series, BMW 7 Series, Cadillac XLR, Infiniti Q45, Jaguar XK-R, Lexus LS430, Mercedes-Benz S-Class, Toyota Sienna XLE (limited availability), and Volkswagen Phaeton.

  • Toyota - "DLCC" (Dynamic Laser Cruise Control)

External links

de:Tempomat fr:Régulateur de vitesse pl:Tempomat


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