* The speedometer shows a steady reading. This means the car is traveling at the same velocity, without accelerating or decelerating.

* The car covers the same distance in the same amount of time. This is the fundamental definition of constant speed - equal distances traveled in equal time intervals.

Important Considerations:

* Constant speed doesn't mean constant velocity. Velocity includes both speed and direction. A car moving in a circle at a constant speed is still accelerating because its direction is changing.

* Real-world scenarios are rarely perfectly constant. Even on a seemingly straight road, there will be slight variations in speed due to factors like road conditions, wind resistance, and driver input.

Examples of constant speed:

* Cruising on a highway with cruise control engaged.

* Driving at a steady pace on a straight road.

* Moving on a treadmill at a set speed.

To summarize, a car moves at constant speed when its velocity remains unchanging over time.