Cruise control (sometimes known as speed control or autocruise) is a system that automatically controls the rate of motion of a motor vehicle. The driver sets the speed and the system will take over the throttle of the car to maintain the same speed.
Modern cruise control (also known as a speedostat) was invented in 1945 by the blind inventor and mechanical engineer Ralph Teetor. His idea was borne 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 Imperial in 1958. This system calculated ground speed based on driveshaft rotations and used a solenoid to vary throttle position as needed.
The driver must bring the car up to speed manually and use a button to set the cruise control to the current speed. The cruise control takes its speed signal from a rotating driveshaft, speedometer cable, wheel speed sensor or from the engine's RPM. 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 or a vacuum driven servomechanism.
All systems must be turned off both explicitly and automatically, when the driver hits the brake or clutch. Cruise control often includes a memory 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 the accelerator is released the car will then slow down until it reaches the previously set speed.
On the latest vehicles fitted with electronic throttle control, cruise control can be easily integrated into the vehicle's engine management system. Cruise controls currently being developed include the ability to automatically reduce speed when the distance to a car in front, or the speed limit decreases. This is an advantage for those driving in unfamiliar areas.
However, cruise control can also lead to accidents due to several factors, such as:
Driving over "rolling" terrain, with gentle up and down portions, can usually be done more economically (using less fuel) by a skilled driver viewing the approaching terrain, by maintaining a relatively constant throttle position and allowing the vehicle to accelerate on the downgrades and decelerate on upgrades, while reducing power when cresting a rise and adding a bit before an upgrade is reached. Cruise control will tend to overthrottle on the upgrades and retard on the downgrades, wasting the energy storage capabilities available from the inertia of the vehicle. The inefficiencies from cruise control can be even greater relative to skilled driving in hybrid vehicles.
Many countries establish that it is illegal to drive within city limits with the cruise control feature activated.
Automatic Braking Type: The automatic braking type use either a radar or laser setup to allow the vehicle keep pace with the car it is following, slow when closing in on the vehicle in front and accelerating again to the preset speed when traffic allows. Some systems also feature forward collision warning systems, which warns the driver if a vehicle in front - given the speed of both vehicles - gets too close (within the preset headway or braking distance).
Dynamic Set Speed Type: The dynamic set speed uses the GPS position of speed limit signs, from a database. Some are modifiable by the driver. * Gpscruise