What optional device allows you to set a constant speed while driving?

Cruise control is an optional device that enables drivers to maintain a steady speed without the need to keep their foot on the accelerator. This feature is especially useful for long-distance driving, as it can reduce fatigue and improve fuel efficiency by allowing the vehicle to operate at a consistent speed. When activated, cruise control takes over the throttle of the car, allowing it to accelerate or decelerate autonomously based on the set speed.

While speedometers display the current speed of the vehicle, they do not control speed. Throttle control and gas pedal holders are not standard phrases used to describe features commonly found in vehicles. Thus, cruise control stands out as the most accurate option for setting and maintaining a constant speed while driving.