The car is moving at constant speed. There are three parts of the motion.
Moves along a straight line at constant speed towards a circular turn.
We see that in this part of motion both the speed and direction of the motion remain constant. As such there is no acceleration as velocity vector does not change.
The car moves along the circular turn at constant speed. We see that the direction of velocity vector changes due to car's circular motion.
Therefore, the car experiences centripetal acceleration which is characteristic of circular motion.
After going round the turn and it moves away along a straight line with constant speed. We observe that this motion is similar as stated in 1 above.
We know that an object which has no acceleration is in equilibrium.
Keeping this definition in view
For motions described in 1 and 3 the car is in equilibrium. In case of motion described in 2 the car is not in equilibrium.